New Trilobites from the Ordovician Beds of New Zealand.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 57, 1927, Page 310

New Trilobites from the Ordovician Beds of New Zealand. By F. R. Cowper Reed, Sc.D., F.G.S., Sedgwick Museum, Cambridge. Communicated by J. Marwick, M.A., D.Sc., New Zealand Geological Survey. [Read before the Wellington Philosophical Society, 9th September, 1925; received by Editor, 21st October, 1925; published separately, 10th December, 1926.] Ogygites collingwoodensis n.sp. (Fig. 1.) Head-shield transversely semicircular, flattened. Glabella very slightly elevated, semicylindrical, about one-third (or less) the width of the head-shield and three-fourths its length, strongly rounded at front end; frontal lobe somewhat inflated, pyriform, with stalk nearly reaching back to occipital furrow, bounded behind by weak, oblique, long lateral furrows marking off large depressed subtriangular basal lobes. Meso-occipital ring flattened, bearing median tubercle; occipital furrow weak. Cheeks and pre-glabella-area flattened; eyes large, semilunar with slightly swollen eye-lobes, situated at about one-third the length and at two-thirds the width of the glabella from its sides. Pleuro-occipital ring narrow, marked off by straight distinct furrow. Genal angles and facial sutures not preserved, but anterior transverse union of facial sutures in front of pre-glabellar area forming a continuous curve. Thorax composed of eight segments, flattened, horizontally extended; axis broad, gently convex, semicylindrical, slightly decreasing in width posteriorly; axial rings simple, flattened. Pleurae horizontally extended and straight as far out as fulcrum, then slightly bent back, recurved and pointed; pleural furrow strong, non-median, slightly diagonal, situated nearer the anterior edge, increasing in width to fulcrum, then rapidly thinning out; anterior part of pleura much narrower and less swollen than posterior part; fulcrum obtusely angular, situated at about two-thirds length of pleurae. Pygidium, large, semi-elliptical, nearly twice as wide as long, very gently convex, with marginal third somewhat depressed and concave. Axis conical, gently convex, about four-fifths the length of the pygidium, tapering more rapidly in anterior part than behind, ending in small blunt slightly elevated tip some distance inside margin; composed of 8–9 distinct rings in anterior two-thirds and of a faintly annulated posterior third; lateral lobes with inner portion gently convex and marked with eight flattened simple unfurrowed pleurae separated by strong interpleural furrows, corresponding with axial rings and slightly angulated at about two-thirds their length, successively decreasing in size and all ending at about two-thirds the width

of the lateral lobes so as to leave a wide, smooth, gently concave undefined marginal area all round the pygidium. Dimensions. A. B. Length of whole trilobite c. 60.0mm. Width of head-shield c.s 41.0mm. Length of head-shield c. 22.0mm. Length of glabella c. 15.0mm. Length of thorax 20.0mm. Width of axis of thorax at front 12.0mm. Width of pygidium c. 41.0mm. c. 40.0mm. Width of axis of pygidium 9.5mm. 8.5mm. Length of pygidium —— 22.0mm. Length of axis of pygidium —— 18.0mm. Locality: Paturau River, Collingwood district, Nelson, N.Z. Remarks: There are two specimens of this trilobite, both from a boulder in the Paturau near Thompson Creek* N.Z. Geol. Surv., Bull. No. 25 (N.S.), Collingwood Subdiv. (1923), p. 22.; one is a complete individual, but the free cheeks, the anterior margin of the head-shield and the posterior end of the pygidium are broken, and the tips of the thoracic pleurae are obscured; the other is a nearly complete but slightly distorted pygidium, with part of its right edge hidden by matrix. The reference of this species to one of the Asaphidae in its broad sense is obvious, and it seems almost indistinguishable from A. (“Basilicus”) kuckersianus Schmidt(1) Schmidt, Rev. Ostbalt. Silur. Trilob. (Mem. Acad. Imper. Sc. St. Petersb., 14, No. 10, 1904) Abt. 5, Lief. 3, p. 25, T. 4, figs. 8–14. from the Kuckerschiefer of the Baltic provinces; the pleural furrow on the thoracic segments sems to be less diagonal and the fulcrum situated further out in this New Zealand form: the eyes also appear to be less closely placed to the glabella, but the head-shield is too imperfectly known for an exact comparison. The other allied Baltic species, “B” kegelensis Schmidt(2) Ibid. p. 29, t. 5, figs. 1–3. and B. lawrowi Schmidt,(3) Ibid. p. 23, t. 4, figs. 1–7. seem less closely related to it. All come from the lower part of the Ordovician. Raymond(4) Raymond, Trans. Roy. Soc. Canada, Ser. 3, Vol. 5, Sect. 4, 1911, pp. 111–120, pts. 1–3. has pointed out that the Basilicus of Schmidt is not the Basilicus of Salter, and that these three Russian species belong to the genus Ogygites (= Ogygia Brongniart). Ogygites has a forked hypostome like Basilicus, but Ogyginus, to which “Ogygia” corndensis Salter, belongs, has an entire hypostome, otherwise the two are considered by him to be almost exactly alike. We do not know the hypostomal characters of the New Zealand species, so that a slight doubt must remain as to generic reference if we accept Raymond's nomenclature and classification. At any rate he is undoubtedly correct in his opinion that the Russian species above-mentioned do not belong to Salter's subgenus Basilicus, of which Asaphus tyrannus Murch. is

the type. The Lower Ordovician species Ogygites birmanicus Reed(1) Reed, Supplem. Mem. Ordov. and Silur. Foss. from Northern Shan States, Palaeont. Indica, N S. Vol. 6, Mem. N. 1, 1915, p. 30, pl. 5, pp. 15–18, pl. 6, figs. 1–4. which the author described from the Hwe Mawng Beds of the Northern Shan States, Burma, may be compared with this New Zealand one, but it is not so closely allied as O. [Basilicus] kuckersianus of Russia. The Yunnan species O. yunnanensis(2) Reed, Ordov. and Silur. Foss. from Yunnan, Palaeont. Indica, N.S. vol. 6, Mem. No. 3, 1917, p. 42, pl. 6, figs. 12–14, pl. 7, figs. 1–8. which the author subsequently described from the Ordovician beds of Pupiao in that country, and considered as very closely allied to the above-mentioned one from Burma is still more closely related to O. collingwoodensis, but the glabella is very imperfectly known, and we may hesitate to regard them as identical. Mansuy(3) Mansuy, Mem. Serv. Geol. Indo-Chine, vol. 7, fasc. 1, 1920, p. 9, pl. 1, figs. 6 a-g. has more recently described a trilobite from the Ordovician of Annam as O. annamensis, and he compares it with O. birmanicus. The pygidium is especially like this new one from New Zealand. This type of trilobite appears to be characteristic of the Lower Ordovician beds, if not confined to them, and we may therefore regard it as probable that the New Zealand species is likewise of the same age. None of the Asaphids described from the Ordovician of Australia are closely related to it. Dionide hectori n.sp. (Fig. 2.) Head-shield transversely semicircular, with the genal angles produced back and acutely pointed. Glabella (incompletely known) subquadrate or oblong and truncated in front, about two-thirds the length of the head-shield, more or less convex, with two (?) pairs of short lateral furrows. Cheeks of head-shield gently convex, more or less inflated, united in front of glabella, crossed by short arched cheekline starting from middle of side of glabella and curving back to join pleuro-occipital furrow some distance out. Surface of cheeks covered with small tubercles and minute pits amongst very delicate reticulating lines; a larger prominent “ocular” tubercle level with front of glabella is situated at about half its width from its side on each cheek. Border of head-shield narrow, rounded, with broader convex concentrically striated doublure. Occipital segment well marked off by furrow from cheeks. Thorax of 6 (or 7) segments. Axis convex, cylindrical, tapering very strongly behind; axial rings with slight lateral swellings. Pleura straight, horizontal to fulcrum which is situated at about three-fourths their length, then bent back and ending in free points; pleural furrow deep, strong; surface of pleurae crossed by transverse wrinklings. Pygidium large, semi-oval or semi-elliptical, flattened, with long narrow conical axis, annulated for whole length and nearly or quite reaching posterior margin; lateral lobes composed of 5–6 elevated strongly furrowed pleurae, separated by well marked fur-

Fig. 1.—a. Ogygites collingwoodensis n.sp. Pygidium. × 2. Paturau R., Collingwood district, Nelson. b. ditto. Nearly complete individual. × 2. Same locality.

Fig. 2.—a. Dionide Hectori n. sp. Nearly complete individual, somewhat distorted × 2½ Taylor-Wangapeka Watershed, Nelson. b. ditto ditto. × 2½. Same locality. c. ditto. Pygidium, obliquely distorted, showing spines. × 4. Same locality. d. ditto ditto. Transversely distorted. × 2½. Same locality. e. ditto. Head-shield and part of thorax. × 2½. Same locality. f. ditto. Portion of thorax, showing ornamentation of pleurae. × 2½. Same locality. g. ditto. Impression of transversely-distorted nearly complete individual. × 2½.

rows and reaching narrow rounded border, the last two pairs subparallel; the first pair wider than all the rest and produced beyond margin into long slender sub-parallel spines about twice the length of the pygidium, curving gently inwards and ornamented with fine longitudinal granulated lines. General surface of pygidium finely tuberculated. Dimensions: Approximate length of trilobite 25–30 mm. Locality: Taylor-Wangapeka Watershed, Nelson, N.Z. Remarks: There are nine fragmentary specimens of this species all more or less distorted, crushed, and imperfect. In one case (Fig. 2, b) we have the impression of the exterior and the cast of the whole individual, but it is much twisted and laterally compressed. In another (Fig. 2, a) we have a nearly complete specimen, poorly preserved, but it shows the pygidial lateral spine on one side. In another (Fig. 2, e) the glabella, cheeks and ocular tubercle are fairly well shown. In a transversely distorted specimen (Fig. 2, d) and in the obliquely crushed one (Fig. 2, a) the genal angles are more or less preserved. The pygidium and its impression with the spines complete are perfect in another case (Fig. 2, c), but the thorax and head-shield are missing. The ornamentation of the cheeks is well seen in Fig. 2, a, and in most of the specimens the fine tuberculation of the thorax and pygidium is visible. In no case is the thorax well preserved and it is difficult to decide whether there are six or seven segments in it, though the larger number would be exceptional. By collecting the evidence from these various specimens we are able to give a fairly complete account of the characters of this new species, the affinities of which seem to be with Dionide richardsoni Reed,(1) Reed, Lower Palaeozoic Trilobites of Girvan (Palaeont. Soc.), pt. 1, 1903, p. 26, pl. 4, figs. 3–8. rather than with D. lapworthi Eth. and Nich.,(2) Ibid. p. 25, pl. 4, figs. 1, 2. D. atra Salt., (3) Reed, Geol. Mag. Dec. 5, vol. 9, 1912, pp. 200–203, pl. 11, figs. 1–6. D. formosa Barr., or D. euglypta Ang. The chief peculiarity and distinctive feature is in the pair of lateral spines on the pygidium which suggests Lichapyge problematica Reed(4) Reed, Lower Palaeozoic Trilobites of Girvan (Palaeont. Soc.), pt. 3, 1906, p. 110, pl. 15, figs. 8–10. from Girvan and recalls some Cambrian genera such as Stephanocare, Drepanura and Teinistion. Dionide is typically an Ordovician genus, and the species to which this New Zealand form is most allied comes from the Upper Bala beds of the Girvan district. Raymond(5) Raymond, Bull. Mus. Compar. Zool. Harvard, vol. 64, No. 2, 1920, p. 274. compares a North American species D. holdoni, which occurs associated with a typical Normanskill fauna, with D. richardsoni, but the pygidium as in that species has no lateral spines. The genus has been also described from Eastern Asia; Mansuy(6) Mansuy, Mem. Serv. Geol. Indo Chine, vol. 1, fasc. 2, Etude geol. Yunnan Orientale pt. 11, Paléont., 1912, p. 37, pl. 6, figs. 2a, 2b. figured a form from the Ordovician of Eastern Yunnan which he referred to the Bohemian species D. formosa Barr., and

the present author(1) Reed, Suppl. Mem. Ordov. and Silur. Foss. from Northern Shan States, Palaeont. Indica, N.S. vol. 6, Mem. 1, 1915, p. 26, pl. 5, fig. 7. described a new species from the Hwe Mawng Beds of the Northern Shan States as D. hybrida which was considered to be allied to the same Euorpean species. But only the head-shield of this Burmese form is known. The genus Dionide is restricted to the Ordovician in Europe, Asia and America, so that on the strength of this evidence these New Zealand beds may be referred to the same period without hesitation. Since the preceding notes were written a further paper on Ordovician trilobites has appeared by Raymond(2) Raymond, Bull. Mus. Comp. Zool., Harvard, vol. 67, No. 1 (April, 1925), pp. 22–29, pl. 1, figs. 16, 17 (D. Holdoni); pl. 6, fig. 9 (D. contrita). in which he describes the four Bohemian species of Dionide and the two from Virginia. The likeness of D. holdoni Raymond, to D. richardsoni Reed is again observed, but the other American species, D. contrita Raymond, has much more numerous segments in the pygidium.