Art. XXII.—Revision of the New Zealand Idoteidæ.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 22, 1889, Page 189

Art. XXII.—Revision of the New Zealand Idoteidæ. By Charles Chilton, M.A., B.Sc. [Read before the Otago Institute, 12th November, 1889.] During the past year I obtained some specimens that revealed a few new facts bearing on the New Zealand Idoteidæ, and, as I had to examine some of the species pretty carefully, I decided to overhaul all recorded from New Zealand; and the following paper is the result. I add one species—viz., Idotea peronii, M.-Edwards—to the list of those found in New Zealand; reduce Edotia dilatata, Thomson, to a synonym of Idotea elongata, Miers; and omit Idotea margaritacea, Dana, as it is, according to Miers, in all probability the same as I. metallica, and in any case it belongs to Australia rather than to New Zealand. At the same time, I am able to settle a few points hitherto uncertain in the synonymy of some of the species, and also to give some additional information regarding them. The species recorded from New Zealand are now eight (8) in number—viz., seven Idoteas and one Cleantis—and of these I have seen all but Idotea marina. It will be interesting to recapitulate what is known of their distribution. Two—I. marina and I. metallica—are almost cosmopolitan, the latter being pelagic in habit, but the former only has hitherto been recorded from Australia; three—I. peronii, I. ungulata, and I. elongata—are widely distributed in the southern seas, I. peronii being known from Australia, Tasmania, New Zealand, and the Cape of Good Hope, I. ungulata from the Indian Ocean, the coasts of South America, Cape of Good Hope, Australia, Auckland Islands, Falkland Islands, and New Zealand, and I. elongata from New Zealand, the Auckland Islands, and the Falkland Islands, but not as yet from Australia, though it is worth noting that the Australian specimens of I. ungulata that I have examined are to a considerable degree intermediate between that species and I. elongata; two species—Idotea festiva and Cleantis tubicola—are known from New Zealand only, the latter apparently being closely allied to C. granulosa, Heller, from St. Paul's; the remaining species, Idotea lacustris, is found in New Zealand only, in a lagoon of fresh water situated close to the ocean, and is probably identical with a species, presumably marine, from the Straits of Magellan. The distribution of these Idoteidœ thus appears to confirm the argument drawn by Professor Parker* “Trans. N.Z. Inst.,” xix., p. 154. from the distribu-

tion of Palinurus in favour of Professor Hutton's theory* “N.Z. Journal of Science,” vol. ii., p. 1. of an antarctic continent, from which the great southern land-masses were stocked. It appears from Miers's “Revision of the Idoteidæ” that there are only five distinct species recorded from Britain, and four, with a doubtful fifth (I. margaritacea), from Australia, so that, according to our present knowledge, the group is better represented in New Zealand. It must not, however, be assumed that our knowledge of the New Zealand forms is by any means complete. Thus, Idotea festiva and Cleantis tubicola are known from single specimens only, and I have in addition a specimen from Lyttelton, which, though too small and immature for identification, certainly does not belong to any of the recorded New Zealand species, but appears to come nearer to Idotea acuminata. I have dissected and examined the three species, I. lacustris, I. ungulata, and I. elongata, in some detail, but the results are not sufficiently important to justify a minute description of their different parts. It is, however, evident that I. ungulata and I. elongata are both much more specialised than I. lacustris, and depart further from the parent species from which the Idoteidæ are descended. Thus, in them the segments of the postabdomen are more anchylosed together; the epimera are not so well developed, and are more or less joined to their respective segments; there is no trace of the second ramus articulating with the basal plate of the operculum, and the same tendency is seen in the mouth parts. Of the two, again, I. elongata is more specialised than I. ungulata. I. peronii appears to come near to the latter species, but I have not examined it in such detail. It is perhaps worth while drawing attention to the fact mentioned below, that the coalescence of the segments of the postabdomen is subject to considerable variation in the same species, and that hence the number of segments of the postabdomen, though a useful character for dividing the species into artificial groups, cannot be relied upon very far to indicate the natural affinities of the different species. After some consideration, I have decided to give full descriptions of all the species. Most of these have already appeared elsewhere, but they are somewhat scattered, and are not easily accessible to New Zealand students. Those which are not original are placed in inverted commas, and have the author's name given at the end in brackets. I have not attempted to give the full synonymy, but I have endeavoured in each case to give those references which will be required by New Zealand students, and also the reference

to. Miers's exhaustive revision of the family, where the full synonymy will be found. I am indebted for specimens to Mr. R. M. Laing, of Lyttelton, to the Trustees of the Australian Museum, and particularly to Mr. G. M. Thomson, who placed at my disposal all the Idoteidæ in his collection, including the types of the species described by him. Idotea Marina. Idotea marina, Miers, “Jour. Linn. Soc. Zoology,” vol. xvi., p. 25 (1881). (The complete synonymy is given in the work quoted.) “Body smooth, moderately convex, and not tuberculated or rugose. Head with the antero-lateral angles very little prominent and rounded, the anterior margin very slightly emarginate. First thoracic segment with the antero-lateral lobes subacute, and not quite reaching to the eyes. Postabdomen about equalling in length the five preceding thoracic segments; terminal segment with the sides straight and slightly convergent to the distal extremity, which is usually more or less tridentate, with the postero-lateral lobes (or lateral teeth) rounded and much less prominent than the median tooth, which is obtuse; there are usually more or less marked indications of a median keel on the dorsal surface of the segment. In other, even adult examples, there are no indications of any except the median tooth. Eyes small. Antennules with the basal joint little dilated, not reaching beyond the penultimate joint of the peduncle of the antennæ in the adult. Antennæ, when retracted, about reaching to the posterior margin of the fourth thoracic segment, with the last peduncular joint a little longer than the preceding; flagellum with not more than twenty joints, and usually about sixteen in the adult. Legs slender; epimera of second to fourth segments more or less oblong, and reaching to the posterior margin of the segment; those of sixth and seventh segments with the postero-lateral angles acute. Posterior plates of the operculum suboblong, longer than broad in the adult. Colour very variable. Length of an adult male does not usually exceed 1 1/6in. (30mm.), breadth rather more than 1/3in. (9mm.).”—[Miers.] The description given above is taken from Miers's “Revision of the Idoteidæ.” The species has a very wide range, being found in Europe, North America, South America (Rio Janeiro), Australia, Java, &c. The occurrence of the species in New Zealand is given by Miers on the authority of a specimen in the Paris Collection (M. Petit). I know the species both through Miers's description and from a specimen from Whitby, England, kindly sent to me by

the Rev. T. R. R. Stebbing; but I have never collected anything like it in New Zealand, and, so far as I know, it has not been taken by any other New Zealand collector. Idotea Festiva. Idotea festiva, Chilton, “N.Z. Jour. of Science,” vol. ii., p. 320 (1884); “Ann. and Mag. Nat. Hist.,” ser. v., vol. xv., p. 123, pl. 5A, figs. 1–3 (1885). Idotea festiva, Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 156 (1886). Body not very convex, oblong-oval; length about two-and-a-half times the greatest breadth. Head transverse, produced upwards and forwards into a rounded prominence divided into two lobes by a median depression, which is continued nearly to the posterior margin; remainder of the head variously sculptured, and with two raised ridges towards the lateral borders. First five segments of the thorax of nearly equal length, sixth and seventh shorter, seventh shorter than the sixth. First segment produced into two rounded anterolateral lobes, which reach to the eyes. Two raised ridges, one near each lateral border, run throughout the whole length of the thorax, and extend nearly to the end of the postabdomen. There is also a less perfect median ridge formed by the posterior portion of each segment being raised into two short converging ridges, like the letter V. This ridge is well marked in the postabdomen, and extends right to the end. Between the lateral ridges and the median ridge, but nearer to the former, are various sculptured markings. Postabdomen about as long as the five preceding segments of the thorax, composed of three distinct segments, the first two short, the third with the lateral sutures of another segment. Postabdomen graddually narrowing until about one-third of its length from the end, when it suddenly contracts and converges with slightly sinuous margins to the extremity, which is subacute. Eyes small, situated on the lateral margin of the head at the posterolateral angle. Antennules* These words were by an error interchanged in the original description. reaching nearly to the end of the third segment of the peduncle of the antennæ;† These words were by an error interchanged in the original description. penultimate segment expanding distally, terminal segment very small. Antennæ‡ These words were by an error interchanged in the original description. as long as the head and first two segments of thorax; last segment of peduncle longer than the preceding, but slightly shorter than the flagellum, which is composed (in the single specimen) of seven joints, of which the first is considerably longer than any of the succeeding. Epimera of only the last three segments of thorax visible in dorsal view; in side view they are all rectangular, those of second and third segments

not reaching to the anterior end of the epimeron of succeeding segment. Opercular plates subtriangular, with slightly-raised border on inner margin; terminal plates very small, triangular, ending acutely. Legs short, not visible in dorsal view. Colour greyish. Length, 10mm.; breadth, (about) 4mm. Hab. Sumner, Canterbury, New Zealand. A single specimen taken on the under-surface of a boulder exposed at low tide. This species appears very distinct, and by the ridges and markings on the body is easily distinguished from other New Zealand species. I have never seen more than the original specimen, and have therefore nothing to add to my original description. Idotea Metallica. Idotea metallica, Bosc, “Hist. Nat. Crust.,” ii., p. 179, pl. xv., fig. 6 (1802). Idotea argentea, Miers, “Cat. N.Z. Crust.,” p. 92 (1876). Idotea metallica, Miers, “Jour. Linn. Soc. Zoology,” xvi., p. 35 (1881); Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 155 (1886). “This species is oblong-oval, moderately convex, the somewhat projecting epimera usually giving, in the adult, a serrated appearance to the sides of the thorax. The head is transverse, with the anterior margin slightly concave; the antero-lateral angles rounded, and but little prominent; near the posterior margin of the head is a deeply impressed arcuated transverse furrow. The surface of the body is more or less rugose; the lateral sutures on the dorsal surface of the postabdomen posterior to the second segment are strongly marked, nearly straight, and directed obliquely upward towards the middle line of the body; the terminal segment is convex, nearly oblong, rounded at the postero-lateral angles; posterior margin square-truncated or very slightly excavated, or with a very obscure median denticle. The eyes are large and prominent. The terminal joint of the peduncle of the antennæ longer than the preceding; the flagellum short, usually 7–10-jointed. The epimera are well developed, with the postero-lateral angles subacute and usually somewhat projecting in the adult; the basal plate of the opercular valves is oblong, with parallel sides; the terminal plate nearly square, but rounded off at its externo-distal angle.”—[Miers.] Length, from 17mm. to 28mm. (Miers). Of this species Miers says, “Apparently a very common and almost cosmopolitan species, probably occurring everywhere except in arctic and antarctic latitudes.” It was introduced originally into the New Zealand catalogue on the authority of Dana, who referred a specimen six lines 13

long, found near New Zealand, to his Idotea argentea, which Miers considers synonymous with I. metallica, Bosc. A specimen undoubtedly belonging to this species was in the collection of Mr. R. Helms, which I examined in 1888. His specimen was certainly taken on the New Zealand coast, probably from Picton, Marlborough. Idotea margaritacea, Dana, is considered by Miers as probably not distinct from I. metallica, though Dana “describes the front as three-toothed, the three teeth very low, one occupying either angle, and the third, which is less distinct, the middle of the front; the outer are subacute and the spaces between low-concave; the body is not quite as much narrowed behind, and the flagellum of the outer antennæ has but four or five joints.” It was captured between Australia and southern New Zealand, 500 miles from Port Jackson, so that it belongs to Australia rather than to New Zealand. It is introduced into the Australian catalogue by Haswell in his “Revision of the Australian Isopoda.”* “Proc. Linn. Soc. N.S.W.,” vol. ix., pt. 4. Idotea Lacustris. Idotea lacustris, Thomson, “Trans. N.Z. Inst.,” xi., p. 250 (1879); ?Miers, “Jour. Linn. Soc. Zoology,” xvi., p. 39, pl. i., figs. 11 and 12 (1881); Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 156. Body narrow elliptical, fairly convex, surface finely punctured. Head with front emarginate, antero-lateral lobes not very prominent, impressed line near posterior margin of the head distinctly marked. First thoracic segment slightly longer than the succeeding, with the antero-lateral angles produced into rounded lobes, those of other segments not produced; succeeding segments subequal in length. Post-abdomen not very convex, as long as the five preceding segments of thorax, composed of two short segments followed by a third bearing two sutures on each side, the posterior suture extending further to the centre than the anterior; end bluntly rounded, margin quite entire. Eyes rather large. Antennules reaching nearly to the end of the third joint of the peduncle of the antennæ, consisting of four joints, the first broad, the other three subequal in length but much narrower. Antennæ when retracted reaching to the posterior margin of the second segment of the thorax, about one-third the length of the body; flagellum as long as peduncle, bearing, in the male, a dense fringe of very short fine setæ. Epimera nearly rectangular, those of second to fourth segments reaching quite back to the postero-lateral angles of the segments, those of

fifth to seventh segments broader and with the postero-lateral angles slightly produced. Terminal plates of the operculum with the exterior margin regularly rounded, very finely serrate at the end. Colour, dark-grey. Length, 15mm.; breadth, 7mm. In New Zealand this species has been found only in Tomahawk Lagoon (fresh water), near Dunedin, where it has been taken in considerable abundance. It appears to be identical with specimens, presumably marine, from the Straits of Magellan; but Miers gives the identification with much hesitation on account of the widely-remote locality at which they were obtained. Unfortunately Miers gives no description of these specimens, simply stating that they agree fairly well with Mr. Thomson's description of I. lacustris. However, the figure that he gives would answer very well for I. lacustris, except that it shows one pair of sutures on the last segment of the postabdomen instead of two; and, judging from the figure, I should say that the Magellan specimens do not differ specifically from I. lacustris. In any case the specimens from the two localities are very closely allied, and would appear to be the remnants of a species probably once abundant and widespread in the southern seas. In that case I. lacustris has probably been preserved in Tomahawk Lagoon owing to its isolation and freedom from competition with other species, which would appear to have supplanted it on the coasts of New Zealand elsewhere. The “dense fringe of very short setæ” on the antennæ is found in the male only. There is no fringe on those specimens (nine in number) which I know to be females, while it is present in all the specimens (thirteen in number) which I know from other reasons to be males. In all of these it is associated with a similar fringe on the second pair of thoracic legs. In some specimens the fringe is not so well developed as in others, and it seems to be developed first on the antennæ and then on the second pair of legs, for in one or two specimens where there is only a slight indication of it on the antennæ there is none at all on the second pair of legs. In all probability these fringes are a secondary sexual character, not developed in the males till they are mature, or perhaps developed only during the breeding-season. In the antennæ the fringe consists of exceedingly fine setæ densely packed, and when fully developed is found principally on the last joint of the peduncle, and on the 6–7 basal joints of the flagellum. In the second pair of legs the fringe is formed of setæ longer than those on the antennæ but of the same kind, and is developed on the inner (lower) surface of the ischios, meros, carpus, and propodos. The setæ forming

these fringes seem to be of the same character as those found on the propodos of the second gnathopod of the males of the Amphipods Nicea fimbriata, G. M. Thomson,* See “Trans. N.Z. Inst.,” xi., p. 236. and Elasmopus subcarinata (= Mœra subcarinata, G. M. Thomson).† See “Annals and Mag. Nat. Hist.,” ser. 5, vol. xvi., p. 368. In this species the males and females closely resemble one another in general shape of the body, and do not present the differences found in I. elongata and, to a much less extent, in I. peronii. As I have already pointed out, this species is not so specialised as I. elongata, &c. In the opercular plates the second ramus is represented by a small membranous plate fringed with long plumose setæ, and the terminal plate also bears a few short setæ at the distal end. In the brood-pouches of the females many young were found. All of these that I have examined resemble the adult animals, except that the seventh thoracic segment was small and without appendages. Idotea Ungulata. Idotea ungulata, Miers, “Jour. Linn. Soc. Zoology,” xvi., p. 52 (1881); Thomson, “N.Z. Jour. of Science,” vol. i., p. 332 (1883); Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 156 (1886). Idotea affinis, Miers, “Cat. N.Z. Crust.,” p. 93 (1876); Thomson, “Trans. N.Z. Inst.,” xi., p. 232 (1879). Idotea excavata, Haswell, “Proc. Linn. Soc. N.S.W.,” vol. vi., p. 2; “Cat. Australian Crust.,” p. 277 (1882). “Body oblong, moderately convex, and nearly smooth. Head with the frontal margin very slightly concave, but with a slight depression in the middle; antero-lateral angles usually but little prominent, smooth above, or with faint indications of an impressed curved line near the posterior margin. Segments of the thorax smooth; the first the shortest, its antero-lateral processes obtuse; the postero-lateral angles of the first to third segments rounded, of the fourth to seventh segments rectangular or acute. Postabdomen somewhat depressed towards its distal extremity, smooth, with lateral sutures indicative of two co-alescent segments; terminal segment with the lateral margins straight to within a short distance of the postero-lateral angles, which are either obtuse or acute; distal end emarginate. Eyes small, black. Antennules not reaching to the distal end of the penultimate joint of the peduncle of the antennæ. Antennæ when retracted not reaching to the posterior margin of the fourth thoracic segment, and often much shorter; last two joints of the peduncle short and subequal; flagellum

longer than the peduncle, with 12 to 28 joints. Epimera rather narrow, in the second and third thoracic segments scarcely occupying more than half the length of the lateral margins, in the fourth to seventh segments occupying their whole length; only the last two epimera on each side have their postero-lateral angles acute. The legs are robust; the fourth to seventh pairs of legs have their posterior and outer angles of the meros and ischium produced, and in adult examples spiniform. The posterior plates of the opercular valves are quadrate and nearly square. The length of the largest example in the Museum collection exceeds 2 ¼in. (58mm.), but average-sized examples measure about 1 ¾in. (45mm.).“—[Miers.] All the specimens that I have collected have been green in colour, and were found on green seaweed. In this species the female, when bearing eggs in the brood-pouch, has the thorax from the first to the fourth segments more or less expanded, as in Idotea peronii. This is the commonest species of Idotea in New Zealand, and is widely distributed in the southern seas, being found in the Indian Ocean, in Australia, on the east and west coasts of South America, Falkland Islands, Cape of Good Hope, &c. As stated by Miers, there is “considerable variation in the length of the flagella of the antennæ, the robustness of the legs, and the depth of the posterior notch of the terminal segment and the acuteness of its postero-lateral angles.” From the account of Idotea excavata, Haswell, given below, it will be seen that, if this species is identical with I. ungulata, there is also some variation in the amount of coalescence of the postabdominal segments, as there is also in Idotea peronii and I. elongata. Miers has already suggested that Idotea excavata, Haswell, is probably identical with I. ungulata,* “Zoology of the ‘Alert,’” p. 311, footnote. and, accepting this suggestion, Haswell has struck out I. excavata from the list of Australian Idoteidæ, though he omitted to put I. ungulata in its place.† “Revision of the Australian Isopoda,” “Proc. Linn. Soc. N.S.W.,” vol. ix., part 4. Through the kindness of the Trustees of the Australian Museum, I have been able to obtain specimens of I. excavata from Portland, Victoria, and to compare them with New Zealand specimens. Both specimens are small, the largest being 20mm. in length. The abdomen consists of a single segment only, scarcely a trace even of a suture being discernible. They thus differ in a marked degree from New Zealand specimens; but, in view of the variation in this respect that I show exists in I. elongata and I. peronii, I am not disposed to place very much importance on this

difference. The epimera, again, though of the same shape as in I. ungulata, are more or less anchylosed to their respective segments, especially in the second, third, and fourth segments, where the dividing-mark is difficult to be seen; in the fifth, sixth, and seventh segments the epimera are anchylosed anteriorly, but free behind. The segments are somewhat separated at the sides, so that the lateral borders are not so continuous as in New Zealand specimens of I. ungulata; the terminal notch is deeper, and the postero-lateral angles more rounded and produced. Altogether, the differences between the specimens are pretty considerable; but, taking into consideration the variation known to exist on these points in this and other species, I am inclined to follow Miers in combining the two species. In all respects except those mentioned the resemblance is very close. It will be seen that in the coalescence of the epimera with their segments, and of the segments of the postabdomen, and in the rounded postero-lateral angles, the Australian specimens resemble I. elongata, and tend to connect that species with I. ungulata. Idotea Elongata. Idotea elongata, Miers, “Jour. Linn. Soc.,” xvi., p. 54 (1881); “Cat. N.Z. Crust.,” p. 93, pl. ii., fig. 3 (1876): Chilton, “N.Z. Journal of Science,” vol. i., p. 517 (1883): Thomson, “N.Z. Journal of Science,” vol. i., p. 332 (1883): Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 156 (1886). Edotia dilatata, Thomson, “Trans. N.Z. Inst.,” xvi., p. 235, pl. xii. (1884); Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 156 (1886). “Body elongate, almost linear, smooth, with the dorsal surface very convex, so that the animal appears almost cylindrical in a dorsal view. Head with the anterior margin scarcely excavated, but with a slight depression in the middle between the antennules; antero-lateral angles not prominent. Segments of the thorax (in the adult male) usually longer than broad, first segment with the antero-lateral lobes prominent and obliquely truncated. Postabdomen about equalling the 3 ½ posterior thoracic segments in length, having usually indications of a lateral suture on each side at some distance from the base of the terminal segment, which is rather depressed above, with subparallel sides, rounded postero-lateral lobes, and a moderately deep rounded notch at its distal end. Eyes small. Antennules scarcely reaching to the distal end of the antepenultimate joint of the antennæ, which have a short peduncle, the last two joints of which are subequal, and each but little longer than the antepenultimate joint; flagellum 18–22-jointed; when retracted the antennæ do not reach

beyond the posterior margin of the fourth thoracic segment. Legs very slender. Epimera scarcely visible in a dorsal view; in a lateral view they are narrow, linear, and the last pair only reach to the postero-lateral angles of the segment with which they are articulated. Terminal plates of the opercular valves somewhat longer than broad, four-sided, with the distal ends truncated or very slightly emarginated. Length of a full-sized male about 2in. (50mm.); breadth about ¼in. (7mm).“—[MIERS.] All the specimens that I have seen were brown in colour when alive, and were found on brown seaweeds. My specimens, of which I have a fair number from Lyttelton, Akaroa, and Brighton near Dunedin, agree well with Miers's description as given above. In some specimens the postabdomen is almost uniarticulate, the dividing-mark being very indistinct; the epimera are difficult to make out, and are usually more or less completely anchylosed with their respective segments. In the female, which has been described as Edotia dilatata by Mr. Thomson, the thorax is “much dilated in the middle, the second, third, and fourth segments being progressively broader and bluntly angled at the sides, fifth suddenly narrowing to less than half the width of the fourth.” In the adult female the plates forming the broad pouch arise from the second, third, fourth, and fifth segments of the thorax. I have one specimen, apparently a young female, with plates of fairly large size on the fifth segment, and very slight indications of plates on the second, third, and fourth; and in this specimen the thorax is slightly broadened. The depth of the notch at the end of the postabdomen varies to some extent. Miers describes it as “a moderately deep rounded notch;” in many of my specimens it might be called a “shallow notch;” but, again, in Mr. Thomson's type-specimen of Edotia dilatata the notch is deeper: the postero-lateral angles are rounded; in Mr. Thomson's figure* Loc. cit., pl. xii., fig. 9. they are shown rather more acutely than they should be. Idotea Peronii. Idotea peronii, M.-Edw., “Hist. Nat. Crust.,” iii., p. 133 (1840); Miers, “Jour. Linn. Soc. Zoology,” xvi., p. 55, pl. ii., figs. 6 and 7 (1881). Idotea stricta, Dana, “U.S. Expl. Exped.,” xiv., Cr. ii., p. 704, pl. xlvi., fig. 7 (1853); Miers, “Jour. Linn. Soc. Zoology,” xvi., p. 62 (1881). Idotea caudacuta, Haswell, “Proc. Linn. Soc. N.S.W.,” vi., p. 1, pl. iv., fig 4.; “Cat. Aust. Crust.,” p. 276 (1882). “Body narrow-oblong rather than oval, not carinated,

nearly smooth. Head etmarginate anteriorly, the middle of the notch straight; the antero-lateral angles rather prominent and rounded. First thoracic segment with the antero-lateral labes rather broad, and not reaching nearly to the eyes. Postabdomen as long as the four or five posterior thoracic segments; terminal segment with two small sutures on each side near the base (indicative of coalescent segments), and with subparallel sides, distal end usually broadly triangulate, and apex subacute. Eyes of moderate size. Antennules scarcely reaching to the base of the antepenultimate joint of the peduncle of the antennæ, with their basal joints considerably dilated. Antennæ with the joints of the peduncle short, the last two subequal, and each but little longer than the antepenultimate joint; flagellum 16–21-jointed, and longer than the peduncle. The epimera are narrow, and in the second, third, and fourth thoracic segments scarcely occupy more than half of the lateral margins; in the fifth segment they reach nearly, and in the sixth and seventh segments quite, to the postero-lateral angles, and in these segments are of a more or less triangulate shape. The legs are very slender. The terminal plates of the opercular valves are three-sided, with their outer margins curving to the distal extremity, which is subacute or blunt. Length of the largest male, about 5/12in. (10mm.); breadth, nearly (48mm.); but most of the specimens are much smaller.—[Miers.] In Miers's “Revision of the Idoteida,” this species is recorded from various parts of Australia, but it has not hitherto been recorded from New Zealand. I first recognised it from a specimen sent me from Lyttelton Harbour by Mr. R. M. Laing; there is a specimen in the Dunedin University Museum from Cape Campbell; and in Mr. Thomson's collection there were two specimens from Waipapa Point, collected by Mr. J. F. Erecson, and a small specimen from Moeraki, collected by Professor Parker. On several occasions I have picked up fragments of this species which had been washed up on the Ocean Beach, Dunedin. These fragments consisted of the skeleton of the postabdomen and one or two posterior segments of the thorax. Curiously enough, I could find no trace of the head and anterior segments of the thorax, though at the same time and at the same place I gathered fragments consisting of the head and anterior segments of the thorax of Pseudaga punctata, Thomson, but could not find any trace of the hinder parts of the body of this species. My fragments of Idotea peronii when gathered were light reddish-pink in colour, but whether this had been the colour of the animals when alive I cannot say; the other specimens, from Lyttelton, &c., are in spirit greyish, sometimes closely covered with small dark spots.

Since this was written I have taken several specimens of this species in rock-pools at Brighton, near Dunedin. They were all taken on red seaweeds, and they closely resembled the seaweed in colour, some of them also having a narrow white streak of varying width down the middle of the back. It is worthy of note that our three commonest species of Idotea are usually found on differently-coloured seaweeds which they closely resemble in colour: Idotea ungulata on green, I. elongata on brown, and I. peronii on red. In his “Revision of the Idoteida” Miers refers to the resemblance between Idotea peronii, M.-Edw., and I. stricta, Dana, but does not unite them because of the uniarticulate postabdomen of I. stricta. It appears, as I shall proceed to show, that this character is subject to variation, and I have therefore united the two species. The conclusion that they both belong to the same species is to some extent confirmed by the fact that, while I had labelled my specimens I. peronii, those in Mr. Thomson's collection, which closely resemble mine, had been labelled by that gentleman as I. stricta. All the New Zealand specimens that I have examined resemble I. stricta in having the postabdomen uniarticulate, but, unlike that species, they have three sutures at the sides; the marks from the first suture, indicating the coalescence of the segments, can be traced further across the postabdomen than those from the second and third sutures, and in some are very faintly indicated almost right across, thus representing the two segments as in I. peronii. Hence they may be considered to be specimens of I. peronii in which the two segments of the postabdomen have more or less completely coalesced. I. stricta, is described and figured by Dana as having a uniarticulate postabdomen, with only one suture on each side, so that the difference of the number of sutures remains to be accounted for: however, as M.-Edwards has described one lateral suture on the terminal segment of the postabdomen of the type-specimen of his I. peronii, while, according to Miers, there are really two present,* it seemed very probable that the sutures vary in distinctness, and that in the specimens examined by Dana the second and third were so indistinct that they were not observed by him; and this view is fully confirmed by an examination of specimens of I. caudacuta, Haswell, kindly forwarded to me by the Trustees of the Australian Museum, Sydney. In the “Zoology of the ‘Alert,’ ”† Miers has already suggested that I. caudacuta, Haswell, is probably identical with I. peronii, M.-Edwards, and before noticing Mr. Miers's *“Jour. Linn. Soc. Zoology,” xvi., p. 56. † P. 311, footnote.

suggestion I had come to the same conclusion from a comparison of the descriptions of the two species. In his “Revision of the Australian Isopoda,”* Mr. Haswell, adopting Miers's suggestion, omitted I. caudacuta from the list without comment. I have now been able to examine specimens of I. caudacuta, Hasw., from Warrnambool, Victoria, and to compare them with my New Zealand specimens of I. peronii, M.-Edw. The result fully proves the truth of Mr. Miers's suggestion, while, as I have already hinted, the specimens present certain features which still further connect I. peronii, and I. stricta. In the specimens from Warrnambool the body is rather more convex and somewhat narrower than in my New Zealand specimen of I, peronii, especially in the postabdomen, and the lateral margins are rounded instead of thinning out, and form a more or less distinct edge. The postabdomen consists of two segments, but, although the division-line is traceable right across with a little difficulty, the two segments are firmly anchylosed together, and the two sutures on the second segment are very indistinct, the first one especially so. The facts already stated show that there is considerable variation in the distinctness of the division-marks on the postabdomen, and there is therefore no difficulty whatever in seeing that Dana's description of I. stricta, as possessing a uniarticulate postabdomen with a single suture on each side, was taken from a specimen in which the division-marks were a little more indistinct than in the Warrnambool specimens. It is perhaps worthy of note that, while in these specimens the postabdomen is composed of two segments, and the following two pairs of sutures are very indistinct, in the New Zealand specimens there is only one segment to the postabdomen, but all three sutures are clearly marked. One of the specimens from Warrnambool is a female bearing eggs in the brood-pouch, and this specimen has the thorax somewhat expanded, though not to anything like the same extent as in Idotea elongata; the lenght is 22.5mm. and the greatest breadth is about 6.5mm. One of the specimens in Mr. Thomson's collection, again, is a female bearing eggs, and in this specimen also there is a slight widening of the thorax; the length is 25mm. and the greatest breadth 7.5mm. In specimens not bearing eggs the proportionate breadth is slightly less than this: thus, one specimen has—length 27.5mm., breadth 7.5mm.; another, length 22.5mm., breadth 6mm.; a third, length 16mm., breadth 4mm. The specimen in Mr. Thomson's collection from Moeraki is a young one, only 5mm. long. The front margin of the head is not emarginate, being even very slightly convex in the *“Proc. Linn. Soc. N.S.W.,” Vol. ix., part 4.

centre;* Compare Miers, “Revision of the Idoteidœ, “Jour. Linn. Soc.” xvi., pp. 56, 57. the seventh segment of the thorax is small, only about half as long as the sixth, and bears no appendages; the three sutures on the postabdomen are clearly marked, the first extending further across the body than the other two; the epimera of the fifth and sixth segments only are visible in dorsal view, and these are small, and the flagellum of the antenna is represented by one joint equal in length to the last joint of the peduncle, and followed by a minute second joint. Cleantis Tubicola. Cleantis tubicola, Thomson, “N.Z. Jour. of Science,” ii., p. 577 (1885); Thomson and Chilton, “Trans. N.Z. Inst.,” xviii., p. 156 (1886); Thomson, “Trans. N.Z. Inst.,” xxi., p. 264, pl. xiv., figs. 5–8 (1888). Body narrow, much elongated, with the sides perfectly parallel. Head with its lateral margin produced downwards into an angular lobe, its front margin nearly straight, its posterior margin produced backwards in the middle into an excavation of the first thoracic segment. First thoracic segment subequal in length to the head, antero-lateral angles slightly produced forward; second segment rather shorter; succeeding segments subequal, hardly exceeding the first in length. The postabdomen nearly equal in length to the five preceding segments of the thorax, apparently consisting of two short segments, the second of which is indistinctly marked and has the posterior margin emarginate, followed by the long third segment, which bears two indistinct sutures on each side; sides parallel except towards the end, where they curve inwards to the extremity, which ends in a deep semicircular notch. Eyes narrow, transverse, placed near the antero-lateral angles of the head. Antennules reaching to the end of the third joint of the peduncle of the antennæ, peduncle three-jointed, flagellum of one long joint, ending in a very short joint and a tuft of setæ; antennæ thick and pediform, as long as the head and first three segments of the thorax; peduncle five-jointed, the first very short, and concealed in dorsal view by the head, the remaining four subequal in length, the flagelequl apparently represented by a single tapering joint about equal to the last joint of the peduncle. The legs short and somewhat compressed, first broader and shorter than the second and third, the third rather longer and more slender than the second, the fourth much shorter than the third and placed transversely, the three last pairs increasing in length posteriorly. Epimera of second to fourth segments indistinct, those of fifth and seventh segments distinct and with the ex-

teior margins produced backwards. The terminal plate of the operculum triangular, about one-third the length of the basal plate. Colour brown, with minute black punctations. Length 15mm. (thorax 11mm., postabdomen 4mm.), the ratio of the length to the breadth being as 11 to 1. Hab. Auckland; found in a tube. The tube in which this animal was found is about 1/2in. long, and appears to be part of the hollow stem of some plant. Whether the presence of the animal in this tube is accidental or habitual is uncertain, but the short legs and strong antennæ seem to favour the latter supposition. The description given above is mainly taken from Mr. Thomson's description, but I have rearranged it and added to it to some extent. He describes four joints in the peduncle and two in the flagellum of the antennæ. In the peduncle there seem to be five joints, but the first is very short, as it usually is in the Idoteida, and hidden in a dorsal view by the head. In the flagellum I can only make out a single joint—a flagellum of a single joint is, in fact, given as one of the generic characters of Cleantis. Judging from the description this species is very close to Cleantis granulosa, Heller, from St. Paul's, but from a tracing of Heller's figure in “Reise der Novara,” pl. xii., fig. 2, kindly made for me by Mr. R. M. Laing, it is evident that the legs in that species are much longer than in C. tubicola.