Some New Genera of the Myalinidae and Pteriidae of New Zealand

Transactions and Proceedings of the Royal Society of New Zealand, Volume 65, 1936, Page 295

Some New Genera of the Myalinidae and Pteriidae of New Zealand By J. Marwick, N.Z. Geological Survey. [Read before the Wellington Philosophical Society, September, 1934; received by the Editor, February 12, 1935; issued separately, December, 1935.] In a paper on The Sequence of Molluscan Life in New Zealand, sent to the Fifth Pacific Science Congress, the writer proposed two new genera, Maitaia and Entomonotis. Formal descriptions and figures were given in an appendix. This and some systematic remarks in the body of the paper were, probably according to policy, cut out by the Editor; but, unfortunately, both new names were left in the text, thus setting a problem in validity. Maitaia trechmanni has a definite bibliographic reference (footnote, p. 947) and is monotypic, therefore it is valid; but Entomonotis has only an indirect reference (to J. P. Smith) and no type is designated, so it is not valid. This confusion has the appearance of careless work on the writer's part, but no proofs, of course, could be submitted owing to distance. In addition to the two genera mentioned, two other new ones are proposed below in order to round off the study of the “Pseudo-monotis” groups of New Zealand. Family Myalinidae. Genus Maitaia Marwick. 1934.Proc. Fifth Pacific Sc. Congress; 1B, p. 948. Genotype (by monotypy): Maitaia trechmanni Marwick. Shell of moderate size, mytiliform, winged posteriorly, equivalve; beaks terminal, slightly raised above the long, straight dorsal margin. Hinge edentulous, margin thickened and flat, and having about three well-defined, longitudinal, ligamental grooves. The shell margins, towards the beaks, thickened and bevelled, and below the beaks, internally, a septal plate was well developed in large shells. Shell substance consisting chiefly of the prismatic layer. Surface with low, rather irregular, concentric waves. Muscle-impressions weak, posterior adductor scar semicircular, of moderate size, placed far back and somewhat nearer the dorsal than the ventral margin. Maitaia trechmanni Marwick. Figs. 1.3. 1870. Inoceramus, Hector, Cat. Colon. Mus., p. 196. 1871. Inoceramus, Davis, Rep. Geol. Explor., 1870–1, p. 107. 1877. Inoceramus, Hutton, Rep. Geol. Explor., 1873–4; p. 34. 1878. ? New genus, McKay, Rep. Geol. Explor., 1877–8, p. 132. 1904. Inoceramus, Park, Trans. N.Z. Inst., vol. 36, pp. 438, 440. 1910. Inorganic, Park, Geology of N.Z., p. 51. 1911. Inoceramus, Bell, Clarke, and Marshall, N.Z.G.S. Bull. 12 (n.s.), p. 19. 1917. Aphanaia sp. cf. mitchelli, McCoy: Trechmann, Geol. Mag. (n.s.). dec. 6, vol. 4, p. 56, pl. 4, fs. 1–4. 1919. Aphanaia, Morgan, N.Z. Jour. Sci. and Tech., vol. 2, p. 34. 1921. not Aphanaia Benson, Aust. Ass. Adv. Sc., vol. 15, p. 18.

1925. ? New genus, Marwick, N.Z. Jour. Sci. and Tech., vol. 7, p. 363, fs. 6, 7. 1934. Maitaia trechmanni Marwick, Proc. Fifth Pacific Sc. Congr, p. 948. Holotype in collection of N.Z. Geol. Survey. Height, 90 mm. (approx.); length, 105 mm. Localities: Geol. Surv. loc. 143, Wooded Peak, Dun Mountain, Nelson (type); Geol. Surv. loc. 1456, 1 mile N.E. Clinton. In most of its characters this shell agrees with Myalina, e.g., the mytiloid shape, longitudinal cartilage grooves, and umbonal septum, the outstanding difference being the prismatic shell. The presence of this septum in the New Zealand fossil has not previously been pointed out, but it shows clearly in Figure 2, and also in Trechmann's figures 1 and 4, though it is not evident from these that the umbos are hollowed out behind the septal plate. In smaller specimens the septum is not wide; however, on the casts some trace of it can generally be seen comparable to the hinge plate of a Mytilus, but, of course, without any teeth. The Clinton specimens are mostly small, though one measures 65 mm. x 65 mm., and there are intermediates, so that the writer is now of the opinion that all can be included in the same species as the Dun Mountain fossils. Further evidence against close relations with the Australian Aphanaia is provided by the specimen shown in Figure 1. The scar of the posterior adductor appears plainly on this cast, situated nearer the dorsal than the ventral margin and of a semicircular shape. The difficulty of obtaining undistorted, complete specimens (or even casts) is largely due to the prismatic structure of the shell-substance and its consequent extreme brittleness. No further evidence as to the age of the Maitai beds has come to light, so that all we can say is that it is upper Palaeozoic. Family Pteriidae. The generic term Pseudomonotis has been used in a very loose sense to include upper Palaeozoic and Mesozoic shells of many shapes and sizes and kinds of sculpture, but all characterised by an anterior byssal ear and notch in the flattened right valve. Some attempts have been made at subdivision, but the major groups, except Oxytoma Meek, have not gained generic recognition. Of course, no rules can be laid down as to what constitutes a genus, and the matter comes in the end to be one of individual taste. Nevertheless, utility must have a strong influence, and it is because of a belief in their strati-graphic and palaeogeographic as well as of their systematic significance, that the new genera here described have been proposed. Owing to the lack of most of the European palaeontological literature, a thorough survey of the different groups cannot be carried out in New Zealand, but since two of them are represented here, one being widespread, their nomenclature has to be dealt with. Pseudomonotis was introduced by Beyrich in 1862, but his paper is not available in New Zealand, so the original species cannot be cited here. The genus soon became widely comprehensive, no

uncommon happening, but an unusual feature is that in strati-graphical and palaeontological text-books any one of three distinct groups may be found illustrating the “genus.” These groups are:— (1) The Permian species related to P. speluncaria Schlotheim (Figs. 5, 6). They are of moderate size, of subtriangular shape, and are not strongly inequilateral, having a relatively short hinge-line and a weak, bluntly rounded, posterior ear. The sculpture consists of more or less irregular, imbricate ridges, tending to differ much in strength on the two valves. (2) The Upper Triassic species such as P. ochotica (Keyserling), subcircularis (Gabb), and richmondiana (Zittel) (Figs. 9, 11). These are large, highly inequilateral shells with a relatively long, straight hinge-line and a well-developed, obtusely angled, posterior wing which has a gently curved posterior margin. The sculpture is regular, consisting of strong radial ribs on both valves, often with interstitial riblets. (3) The Jurassic species belonging to the group of P. echinata W. Smith (Figs. 7, 8). These are rather small shells, having a sub-quadrangular outline and a very long, straight hinge-line. The posterior ear is well developed, having a deeply concave posterior margin which makes an acute angle with the dorsal margin. In addition to these, a number of species, now attributed to Pseudomonotis, have been described from the Lower Triassic of Europe. They are rather small, plump shells having a fairly long hinge-line and a very small byssal ear. The sculpture consists of fine radials, not imbricate, and tending to become obsolete. These have already been subdivided into two groups, Claraia Bittner, and Eumorphotis Bittner, presumably as sections of Pseudomonotis, which is the rank given by Diener. The chief link used to bind these and other groups in the one genus is the byssal ear and notch in the right valve, but other groups such as the Pectens and Buchias, possess similar structures. Moreover, the different groups of “Pseudomonotis” present important differences in the arrangement, not only of the anterior ear and notch, but also of the ligament. It is therefore clear that, as generally conceived, Pseudomonotis includes widely separated lineages, and generic ranks for the chief groups indicated is more in accord with systematic and stratigraphical demands. 1. Genus Pseudomonotis Beyrich. 1862. Zeits. deutsch. geol. Gesell., Bd. xlv, p. 9. Genotype (by subsequent designation, Stoliczka, 1870, p. xxi): Gryphites speluncarius Schlotheim, Zechstein, Europe. Stoliczka, as early as 1870, designated as type of Pseudomonotis the Permian P. speluncaria (Schloth.), and in this he was followed by Fischer (Manuel, p. 954). Pseudomonotis must therefore always include the short-hinged group of Permian species which have been recorded from Europe (P. speluncaria, radialis Phil., kazanensis Vern., garforthensis King), India (P. radialis, kazanensis, garforth-ensis) and North America (P. hawni Meek and Hayden). Meek, who was unaware of the prior Pseudomonotis, in 1864 proposed for

this group Eumicrotis, genotype Monotis hawni Meek and Hayden, a Kansas Permian species having sculpture and shape similar to those of speluncaria. His name therefore falls as a synonym of Pseudo-monotis and cannot be used for any of the other groups mentioned. J. P. Smith (1927, p. 120) gave the type of Pseudomonotis as P. ochotica, stating that “Beyrich named no type… but made it clear that he meant this particular group.” Stoliczka's (and Fischer's) designation, however, appears to be quite valid and consequently is “not subject to change.” (Internat. Rules, Art. 30, 11, g.). Subgenus Claraia Bittner, 1901. Jahrb. Geol. Reichanst., 50, p. 568. Genotype: Posidonomya clarae Emmrich, Lower Triassic, Europe. Concerning the relationship of this group the writer is not in a position to give a useful opinion. In passing, however, it may be mentioned that Posidonomya clarae Emmrich is given by Sherborn as a nomen nudum. Further, Diener (1913, p. 42), recording four species from the Himalayas, gave the date of Bittner's paper as 1900, but the Zoological Record gives it as 1901, probably the actual date of publication. Subgenus Eumorphotis Bittner, 1901. Jahrb. Geol. Reichanst., 50, p. 566. Genotype: Pseudomonotis telleri Bittner, Lower Triassic, Europe. Diener (1913, p. 44) recorded 3 European species (one doubtfully) from the Himalayas. 2. Genus Entomonotis nov. 1934. Marwick, Proc. Fifth Pacific Sc. Cong., p. 949, nomen nudum. Genotype: Monotis salinaria var. richmondiana Zittel, Noric, New Zealand. Shell of moderate to large size, outline obliquely sub-oval inequivalve, left valve moderately to well inflated, with high, narrow, strongly incurved, slightly prosogyrous umbo; right valve flat to gently inflated, umbo low, scarcely rising above the hinge-margin. Both valves have a prominent posterior wing, merging with the disc and obtusely angled at the junction of the long, straight dorsal and the gently curved posterior margins. Left anterior wing very weak, but right anterior wing well developed, though not clearly defined except by the sculpture, because of its gently convex margin. Sculpture of strong, regular, radial ridges on both valves, interstices generally with riblets of a higher order. Right valve, between umbo and anterior wing, bears a narrow, thin, spoon-shaped ear separated from the anterior wing by a deep byssal notch. The ear is concave and has narrow margins; it is obliquely set, well over-lapped by the anterior wing, and bears on its exterior surface bounding the notch about 6 sharp, well separated, curved ridges. Lower side of notch formed by down-turned margin of anterior wing and bearing longitudinal ridges. Hinge-area narrow, edentulous. Ligament set in a much extended, scarcely excavated, triangular area which bears

Fig. 1.—Maitaia trechmanni Marw. X 1; loc. 143, Dun. Mt. Internal cast showing muscle scar. Fig. 2.—Maitaia trechmanni Marw. X 1; plasticene cast of holotype. Fig. 3.—Maitaia trechmanni Marw.; ideal reconstruction. Fig. 4.—Entomonotis richmondiana (Zitt.); X 4; byssal notch from within, showing the curved ridges on the lower side of ear.

Figs. 5, 6.—Pseudomonotis speluncaria (Schloth.); genotype (after King X 1). Figs. 7, 8.—Echinotis echinata (W. Smith) n.gen.; (after Morris & Lycett, X 2). Figs. 9, 11.—Eutomonotis richmondiana (Zitt.) n.gen. X 1; Mount Heslington. Figs. 10, 12.—Otapiria marshalli (Trech.) n.gen. X 1; Hokonui Hills. Figs. 13, 14.—Entomonotis richmondiana (Zitt.) X 4; left hinge from in front and from above, showing actual shell, 88 Valley. Figs. 15, 16, 17.—Entomonotis richmondiana (Zitt.) X 4; plasticene casts of left hinges, 15 and 17 from in front, 16 from above.

Figs. 18–24.—Entomonotis richmondiana (Zitt.) X 4; plasticene casts of right hinges; 23 from in front, the rest from above. Figs. 25–27.—Echinotis echinata (W. Smith), enlarged (after Pompeckj); right valve. Figs. 28, 29, 32.—Otapiria marshalli (Trech.) X 8; from above, from in front, and from obliquely anterior. Figs. 30, 31, 34, 35.—Otapiria marshalli (Trech.) X 8, left valve casts, 35 from above, rest from in front. Figs. 33.—Entomonotis richmondiana (Zitt.) X 4; from obliquely anterior.

about 4 (3 to 6) parallel, longitudinal grooves. Hinge-area in left valve with a prominent bulge just in front of the beak, merging into a deep anterior sinus in the hinge-margin. The anterior byssal ear of the right valve should not be confused with the anterior wing which, like the posterior wing, is the flattened extension of the disc bordering the dorsal margin. The New Zealand species, P. richmondiana, has been chosen as type instead of the older ochotica Keyserling because duplicates will be more readily available and the possibility seems greater of obtaining specimens that will show further details of the hinge and musculature. Owing to the very thin shell, specimens showing the hinge-details clearly are extremely rare; and, although a considerable amount of material was examined during the present survey, no example was found showing any trace of a muscle scar, nor was a complete hinge of either valve seen. Even casts of the hinges were difficult to get, largely owing to the hinge-area being so narrow that the break in the enclosing rock, necessary to reveal the imprint, generally runs irregularly along it and destroys it. Also the matrix of many of the Entomonotis beds is too coarse to preserve the finer hinge details. However, sufficient examples were obtained to show the essential hinge-features, though further material may modify the present results to a small extent. Wilckens (1927, p. 12, pl. 1, fig. 23c) has figured and described the hinge as possessing “two narrow teeth, directed posteriorly at a sharp angle,” but what he took for teeth is the imprint of the right anterior ear on the internal cast owing to the right valve having slipped down slightly from its normal articulation with the left. The hinge is undoubtedly edentulous, as is to be expected from the systematic position of the genus. King's figures of P. speluncaria (1850, pl. 13) show the right valve with a short, straight hinge-line and an anterior ear and notch rather like that of a Chlamys, that is, the ear is in the same plane as the disc and is not overlapped by it. The byssal ear of Entomonotis, on the other hand, is set obliquely to the disc and is somewhat overlapped by the anterior wing, which, moreover, is turned down to form a submargin parallel to the ear. Waagen (1881, pl. 22, f. 3c) has published a figure showing the left hinge of P. kazanensis, from the Permian of the Salt Range. This hinge has an altogether different shape anteriorly from that of Entomonotis, thus furnishing another reason in favour of generic separation. Occasional specimens, both right and left valves, on which the surface markings are well preserved bear regular, well spaced, concentric ridges which are stronger on the radial ribs than in the interspaces. The small, curved, transverse ridges on the lower anterior surface of the byssal ear probably functioned as a ctenolium. Prints of these ridges (Fig. 4) are to be seen in most specimens that show the byssal ear or its cast; but owing to their concealed position they have generally escaped attention. The only reference to them found was that of Teller, whose fig., 9, pl. 18, shows the ridges cearly and

bears the legend “mit gestreiftem Byssohr.” One specimen from Mount Heslington (Fig. 33) which still has some of the shelly surface remaining also shows a ctenolium on the lower side of the notch, the teeth being apparently raised continuations of growth striae. The earlier of these ridges are transverse, but the later ones run obliquely along the notch, and are thus almost at right angles to the ridges on the ear. Entomonotis richmondiana (Zittel). Figs. 4, 9, 13–24, 33. 1864. Monotis salinaria var. richmondiana Zitt., Novara Expd. Geol., Th. 1 bd., 2 abt., p. 26, pl. 6, fs. 1, a-e. Entomonotis generally occurs in great profusion, at many places forming bands 10ft. to 20ft. thick, crowded with casts of the valves. These present a bewildering range of form and sculpture, so that although systematists have tried to separate them into carefully described varieties, the results are not satisfactory. Thus, when Keyserling first introduced his Avicula ochotica he described three varieties, major, media, and minor. Teller (1886, p. 116) considered these as not tenable, but he proposed the new varieties densistriata, sparsicostata, eurhachis, ambigua, and pachypleura, remarking that Keyserling's var. major was very close to his own densistriata and pachypleura. According to Trechmann, Frech, whose work is not available in New Zealand, considered “that the three circum-Pacific species… ochotica, richmondiana, and subcircularis are varieties of one and the same shell. He believes that P. richmondiana occurs in two forms, and figures and describes a new form as var. truncata.” Trechmann (1918, pp. 191–196) recognised P. ochotica as occurring in New Zealand represented by the five varieties of Teller, and in addition he described the new variety acutecostata. He, however, considered richmondiana as a separate species occurring at a slightly lower horizon in the Noric than ochotica. Further, Trechmann identified as Monotis salinaria Bronn, in a limestone from Okuku, Canterbury, shells which are undoubtedly Entomonotis. Several right valves have now been excavated, and all show the characteristic byssal notch. Monotis must therefore be deleted from New Zealand lists and the varieties intermedia and hemispherica Trechmann (p. 196) must be added to the list of richmondiana varieties. The variety hemispherica, for which the original of Trechmann's pl. 20, fig. 3 is hereby designated lectotype, has the broad, smooth, simple ribbing of pachypleura, but is small, and more inflated than Teller's figured types. Variety intermedia, for which the original of Trechmann's pl. 20, fig. 1 is hereby designated lectotype, closely agrees with the typical richmondiana. It is difficult to decide just how to name the New Zealand examples of Entomonotis. Recent collections by officers of the Geological Survey from Mokau, Kawhia, and Eighty-eight Valley do not confirm Trechmann's idea that two distinct species, ochotica and richmondiana can be distinguished at different horizons, but in the absence of actual specimens from Siberia, it is perhaps hazardous to form a decided opinion as to the relationship of the New Zealand species to ochotica. Judged by Teller's figures, the two groups are doubtfully separable specifically; but the geographic facts should probably be taken as a guide. Accordingly richmondiana is here

recognised as specifically distinct from ochotica, the many varieties identified by Trechmann being considered as forms of richmondiana, but not, of course, under Teller's varietal names. Since most, if not all, of these varieties occur promiscuously in the one horizon, they do not appear to be worth systematic recognition. One form, however, is worth special notice, that is the very large, flat, thin-shelled “variety” from Garden Gully, identified by Trechmann (pl. 19, fig. 1) as ochotica var. densistriata Teller. At the only locality where this shell has been found it occurs plentifully and dominates the other varieties. Many specimens are over 80 mm. long, and some over 100 mm. The sculpture has ribs of the fourth order, a development not mentioned by Teller in his description of densistriata. This, combined with the large size, suggests that the form may have systematic value. Trechmann (p. 193) has already remarked on the resemblance of this shell to the Western American subcircularis Gabb. 3. Genus Echinotus nov. Genotype: Avicula echinata W. Smith, Middle Jurassic, Europe. Shell rather small, inequivalve, outline subquadrate, left valve well inflated, right valve flat. Both valves have a prominent posterior wing, acutely angled at its junction with the long, straight dorsal and strongly concave posterior margin. Anterior wings weak, right byssal ear well developed, oblique, considerably overlapped by the anterior wing. Sculpture discrepant, right valve with strong, regular, radiate ridges, left valve smooth. Hinge-area edentulous, with a well excavated, triangular ligament-pit. Left hinge having a thickening below the umbo with a gentle sinus anteriorly and bounded by the ligament posteriorly. Echinotis echinata (W. Smith). Figs. 7, 8, 25–27. 1817. Avicula echinata W. Smith, Strat. Syst. org. Foss., p. 67. Good figures of the hinge have been published by Pompeckj (1901, pl. 15, fs. 1, 4, 7, 11, 15, 19). These show that the hinge, while built on the same general plan as that of Entomonotis, yet presents important differences. Entomonotis has a wide, scarcely excavated ligament-pit which bears several well incised parallel grooves, but Echinotis has a much narrower, well excavated pit which is not regularly grooved. The left hinges of both Entomonotis and Echinotis bear a prominent thickening immediately anterior to the ligament; but the disposition of this and also of the rest of the hinge differs in the two groups. For instance, in Entomonotis the thickening merges into the ligamental area and is itself finely striated; in Echinotis it is sharply separated from the ligament. The specimens of E. echinata recorded by Trechmann (1923, p. 271) are the only ones that have been yet found in New Zealand. Since they are rather poor casts, the identity is not beyond doubt, but is accepted by the writer, who, however, wrongly identified as “P. echinata (?)” shells from the Awakino Valley (Henderson and Ongley, 1923, p. 24). The resemblance is only superficial, the smooth right valves have no byssal ear, and the generic relation may be with Placunopsis.

The Jurassic shell described and named by Trechmann (1923, p. 270, pl. 15, fs. 6–9) as Pseudomonotis marshalli was recognised by him as aberrant and not closely related to any of the known species of Pseudomonotis (sensu lato). The hinge of a comparatively well preserved right valve has now been excavated, and also casts of left hinges have been secured. These show much in common with Entomonotis and Echinotis; but the differences of hinge detail, of surface sculpture, and of shape indicate considerable divergence of the stock, and entitle it to generic rank. 4. Genus Otapiria nov. Genotype: Pseudomonotis marshalli Trechmann, Middle Jurassic. New Zealand. Shell of moderate size; regularly obliquely ovate, little inflated, inequivalve, right valve almost flat. Posterior wing well developed, anterior of shell generally produced, but having a short dorsal margin and a narrowly convex outline and so no defined wing. Sculpture of numerous, close, radial riblets. The right valve has, immediately in front of the umbo, a small ear, the finely striated upper surface of which is a continuation of the ligamental area. This surface tapers anteriorly, and its raised margins unite to form a thickened, rounded, upper border to the ear, which below this is concave, and is overlapped considerably by the disc with its straight, erect, dorsal margin. Hinge-area narrow, edentulous. Ligament set in a strongly and regularly grooved triangular ligament-pit, the base of which is about half the length of the posterior dorsal margin. Left valve with the hinge-margin sinused upwards and inwards immediately in front of the umbo, but further forward the margin projects outwards and bears several deep grooves. Otapiria is nearest to Entomonotis in general characters and may be the Jurassic descendant of that stock. Otapiria has much finer sculpture, an exceptionally ovate shape, and the hinge of the left valve has a sinus instead of a projection immediaetly in front of the ligament and beak. The ligament-pit is more deeply entrenched than that of Entomonotis, thus resembling Echinotis, but the well incised parallel grooves increase the affinity with Entomonotis. The anterior ear of the right valve of Otapiria shows important differences from that of Entomonotis, being set more in the plane of the disc, the upper edge of which is consequently not bent inwards. Otapiria marshalli (Trechmann). Figs. 10, 12, 28–32, 34, 35. 1886. Pholadomya sp. Hector, Cat. Ind. and Col. Exhibit., append. p. 69, f. 34, No. 4. 1923. Pseudomonotis marshalli Trech., Q.J.G.S., vol. 79 (3), p. 270, pl. 15, fs. 6–9. Localities: Slopes of Flag Hill, Hokonui Hills, Trechmann, type. G.S.343 “Upper ‘Plagiostoma’ beds,” west face, Flag Hill. G.S.344 “Upper ‘Plagiostoma’ beds,” north face, Flag Hill. G.S.345 “Upper ‘Plagiostoma’ beds,” west face, Bastion Hill. G.S.348 “Higher part Lower ‘Plagiostoma’ beds,” Otapiri Ck. G.S.349 “Lower part Lower ‘Plagiostoma’ beds,” Otapiri Ck. All of these localities are in the Hokonui Hills, Southland (see McKay, 1878, Rep. Geol. Expl. during 1877–8, vol. 11, pp. 83, 84). The Plagiostoma of Cox, and McKay's “Plagiostoma beds” probably referred to Otapiria.

Summary. Proposed Classification. Age. Previous Classification. Maitaia trechmanni Marwick Upper Palaeozoic Dun Mt. Inoceramus Aphanaia cf. mitchelli McCoy Entomonotis richmondiana (Zittel.) Upper Triassic Pseudomonotis Echinotis echinata (Smith) Middle Jurassic Pseudomonotis Otapiria marshalli (Trechm) Middle Jurassic Pseudomonotis References. Diener, C., 1913. Trias. Faun. of Kashmir, Pal. Indica, n.s., vol. 5, mem. 1. Henderson, J., and Ongley, M., 1923. Geol. of Mokau Subdiv., N.Z. Geol. Surv. Bull., 24. King, W., 1850. Monograph of Permian Foss. of England, Palaeontograph. Soc. Meek, F. B., 1864. Amer. Journ. Sci. and Arts, 2nd Ser., vol. 37. — 1876. Invert. Cret. and Tert. Foss. Upp. Missouri, U.S.G.S. Territories, vol. 9. Pompeckj, J. F., 1901. Ueber Aucellen U.Auc-ahnl. Formen, N. Jahrb. f. Min. Geol. Pal., b. bd. 14. Smith, J. P., 1927. Upper Trias. Marine Invert. Faun, U.S.G.S. Prof. Pap. 141. Stoliczka, F., 1870. Cret. Faun. of S. India, Pelecypoda, Pal. Indica, ser. 6, vol. 3. Teller, F., 1886. Die Pelec. Faun. v. Werchojansk in Ostsiber.; Arktis. Trias-faun., E. Mojsisovics, Mem. l'Acad. Imp. Sc. St. Petersb., 7th ser., tome 33, no. 6. Trechmann, C. T., 1917. Age of the Maitai Ser. of N.Z., Geol. Mag., n.s., dec. 6, vol. 4. — 1918. Trias of N.Z., Quart. Journ. Geol. Soc., vol. 73, pt. 3. — 1923. Jurassic Rocks of N.Z., Quart. Journ. Geol. Soc., vol. 79, pt. 3. Waagen, W., 1881. Salt Range Fossils, Productus Limestone, Pelecypoda, Pal. Indica, ser. 13, vol. 1, pt. 3. Wilckens, O., 1927. Pal. of N.Z. Trias, N.Z. Geol. Surv. Pal. Bull., No. 12.