Description of Tertiary Brachiopoda from New Zealand.
[Read before the Otago Institute, 8th July, 1930; issued separately, 30th September, 1931.]
Recent field-work in various parts of New Zealand has resulted in the discovery of several new species of Tertiary brachiopods. Some of these are here described.
Rhizothyris labiata n. sp. (Pl. 21, Fig. 2).
Description.—Shell large for the genus, broadly elliptical, sides convex, slightly tapering in front but broadly truncated. Ventral valve strongly convex, with the greatest convexity about the posterior third; dorsal valve moderately convex. Anterior commissure incipiently sulcate. Beak of medium length, suberect. Beak-ridges sharply carinate, merging into the sides. Foramen permesothyrid, labiate, oval, oblique. Symphytium of moderate height, but very wide. Lateral palintropes narrow. Hinge-line broad, but gently curved. Shell smooth, except for growth-lines. Punctation fine and dense.
Hinge-teeth large and strong, supported by huge, swollen bases. Ventral muscular impressions large. Dorsal valve greatly thickened posteriorly. Dental sockets large and deep. Inner socket ridges indistinctly fused against the crural bases anteriorly, and running back as a thin plate to coalesce with the posterior part of the cardinal process. The two structures project, in ear-like processes, beyond the dorsal hinge-line. Crural bases enormously swollen, divided medially by a groove running from the top of the septum to the base of the cardinal process. The latter is very large, and completely fills the hinge-trough. The upper (ventral) surface is flat, but two ridges run back to the ears. Laterally there are grooves bounded by the sides of the cardinal process, the posterior surface of the crural bases, and the inner sides of the socket ridges. Between the ear-like processes and resting on the posterior surface of the cardinal process, is a striated muscular pit. The crura are attached to the crural bases, close together, above the septum. The latter is short, considerably thickened below, but plate-like above, and at its anterior end. It is fused posteriorly against the crural bases, but does not bifurcate. Muscular impressions in a deep pit. Loop magellaniform, extending two-thirds of the whole length.
Dimensions of holotype: Length, 45 mm.; breadth, 38 mm.; thickness, 24 mm.
Type locality: Clifden, Southland. Horizon C on the east side of the Waiau River.
Material: The species is very abundant and perfectly preserved.
Mr F. J. Turner, of Otago University, to whom I owe the pleasure of describing this fine species, collected some 30 specimens. It also occurs, but more rarely, in horizons B and D on the same side of the river. Horizons B, C, and D are, as a whole, the equivalent of Band 7 of Dr Finlay's papers on Clifden. The age is the same as that of the Uppermost Mount Brown limestone of the Weka Pass district.
Affinities.—R. labiata n. sp. differs from R. elliptica Thomson in shape, and in the character of the foramen. It is not likely to be confused with any other species.
Rhizothyris longitudinalis n. sp. (Pl. 20, Fig. 5; Pl. 22, Figs. 5–7).
Description.—Shell elongate-elliptical, hinge-line broad and little curved, sides very slightly convex, front rounded. Valves moderately convex. Anterior commissure almost straight or incipiently sulcate. Beak prominent, nearly straight, little produced dorsally of the hingeline. Beak-ridges pronounced, forming an obtuse-angle with the sides. Foramen permesothyrid, of moderate size. Symphytium high and wide.
Dimensions of holotype: Length, 50 mm.; breadth, 34 mm.; thickness, 23 mm.
Type locality: Clifden Quarry, Clifden, Southland, in a rubbly, yellow-brown limestone. The species is comparatively rare.
Affinities.—R. longitudinalis n. sp. agrees closely with R. elliptica Thomson (1920, p. 372, Pl. 22, Fig. 1; Pl. 23, Fig. 3), but differs in being more elongate. With R. elongata Thomson (1920, p. 372, Pl. 22, Fig. 11; Pl. 23, Fig. 11) the new species agrees in elongation, but differs in being broadly rounded anteriorly. Both R. elliptica Thomson and R. elongata Thomson are associated with this species at Clifden.
Rhizothyris rhizoida (F. W. Hutton 1905). (Pl. 20, Fig. 2; Pl. 22, Fig. 4).
1905. Bouchardia rhizoida Hutton. Trans. N.Z. Inst., 37 (June), p. 480, Pl. 40, Fig. 7.
1915.Rhizothyris rhizoida (Hutt.) J. A. Thomson, Trans. N.Z. Inst., 47, p. 398, text-fig. 5 a-b. (5a = holotype). (Not 5d = R. elliptica Thomson 1920).
1927. Rhizothyris rhizoida (Hutt.) Thomson, N.Z. Board Sci. & Art., Man. No. 7, pp. 278–9, text-fig. 93 a-b.
Description of topotype: Shell of medium size for the genus, triangular, sides gently convex, rapidly tapering, front pointed. Hinge-line broad, gently curved. Beak very prominent, erect, produced dorsally of the hinge-line. Beak-ridges strongly carinate, forming an obtuse-angle with the sides. Foramen of moderate size, permesothyrid, labiate. Symphytium high and wide. Lateral palintropes prominent, almost flat. Anterior commissure nearly straight but incipiently sulcate. Both valves strongly convex. Shell smooth. Punctation fine and dense.
Dimensions of topotype: Length, 36 mm.; breadth, 28 mm.; thickness, 21 mm.
Type locality: Weka Pass district. (Probably from the Main Mount Brown limestone which may hereafter be considered the type horizon).
Remarks.—J. A, Thomson (1920, p. 371) stated that shells exactly matching the holotype are rare; and he enlarged the species “to include those shells intermediate in elongation between R. scutum and R. elongata (both of Thomson 1920) which are moderately elongate, with a slightly curved hinge-line nearly the breadth of the shell, and a marked taper. These shells are moderately to strongly convex, and always show some folding.”
The writer is at present unable to follow Thomson in this redefinition, and would restrict rhizoida to shells agreeing with the holotype. The shell figured by Thomson (1920, Pl. 22, Fig. 6) is not typical.
As thus restricted R. rhizoida is known to me from two localities only, viz., the Main Mount Brown limestone, Weka Pass; and Clifden Quarry, Clifden, Southland, in a rubbly limestone. Both horizons are of Hutchinsonian age.
Rhizothyris trigonalis n. sp. (Pl. 20, Fig. 3; Pl. 22, Figs. 1–3).
Description.—A Rhizothyris closely related to R. rhizoida (Hutt.), but with a rather wider hinge-line, a much shorter beak, a low wide symphytium, and a small foramen.
Dimensions of holotype: Length, 34 mm.; breadth, 29.5 mm.; thickness, 19 mm.
Type locality: Limehills, Winton. Collected by Dr F. H. McDowall. The species also occurs in the Hutchinsonian greensands of Hutchinson's Quarry, Oamaru.
Pachymagas turneri n. sp. (Pl. 21, Fig. 1; Pl. 22, Figs. 8–10).
Description.—Shell large for the genus, broadly ovate, sides convex, front tapering but broadly truncated. Valves strongly and evenly convex. Hinge-line broadly rounded. Ventral valve with a distinct, wide, flat keel. Anterior commissure with a broad shallow sulcation. Beak large, erect, little produced dorsally of the hinge-line. Foramen mesothyrid, attrite, rather large. Beak-ridges not strongly carinate. Symphytium high but narrow. Lateral palintropes wide, concave. Punctation fine and dense.
Dimensions of holotype: Length, 56 mm.; breadth, 45 mm.; thickness, 28 mm.
Type locality: Rubbly limestone, Clifden Quarry, Clifden, Southland.
Remarks.—The holotype was the only specimen of this species collected by the writer, but Mr F. J. Turner, of Otago University, has since obtained a second perfect example from the same locality.
Affinities.—P. turneri n. sp. is a very distinct species which does not seem to be closely related to other members of the genus known from New Zealand.
Terebratella clifdenensis n. sp. (Pl. 20, Fig. 1).
Shell of medium size, broadly ovate, greatest width slightly posterior to the middle line, sides rather strongly convex, tapering anteriorly, and narrowly truncated in front. Ventral valve strongly carinate from the umbo to the anterior margin; dorsal valve flattened with a shallow median trough. Anterior commissure strongly sulcate. Beak prominent, suberect. Beak-ridges well defined. Foramen large, oval, submesothyrid. Deltidial plates almost conjoint, separated by a groove from wide, slightly concave palintropes. Punctation fine and dense. Shell smooth, except for growth-lines. Interior unknown.
Dimensions of holotype: Length, 27 mm.; breadth, 22 mm.; thickness, 12 mm.
Type locality: Clifden, Southland, Band 6A.
Remarks.—A very distinct new species, of which two specimens only are known. The holotype was collected by the writer, a paratype by Dr H. J. Finlay. This species may prove to belong to Magella which differs from Terebratella only in loop characters.
Tegulorhynchia sublaevis (J. A. Thomson, 1918). (Pl. 20, Fig. 4).
1918. Hemithyria sublaevis Thomson, in J. Park, N.Z. Geol. Surv. Bull. No. 20, p. 117, not figured.
1923. Tegulorhynchia sublaevis (Th.), Chapman and Crespin, Proc. Roy. Soc. Vict., 35 (N.S.), pp. 188–9, not figured.
Description (Based upon a manuscript diagnosis by J. A. Thomson; and on study of topotypes).—Shell small, slightly broader than long, sides rounded, front somewhat variable but not departing much from a straight line. Dorsal valve strongly convex, especially near the umbo, with a broad, slightly raised, median anterior fold. Ventral value much less convex, flattened anteriorly, with a broad median anterior sinus. Anterior commissure strongly uniplicate. Hinge-line broadly rounded. Beak short, bluntly pointed, erect. Foramen rather large, hypothyrid. Deltidial plates disjunct. Surface ornament consisting of a variable number of very low, rather fine costae, which are not scaly and are often almost obsolete. The multicostation is best expressed on young shells, which are relatively less convex, and possess more acute beaks. The growth-lines are prominent on older shells and are crowded anteriorly. Internal details as for the genus. (See Thomson, 1927, pp. 152–3).
Dimensions of holotype: Length, 10 mm.; breadth, 10–5 mm.; thickness, 7 mm.
Type locality: Everett's Quarry, Kakanui. The species is abundant in the Kakanui limestone.
Age: Upper Ototaran.
Affinities.—T. sublaevis (Thomson) belongs to the same group as T. depressa (Thomson), but differs from that species in being more narrowly and strongly folded; and in possessing non-imbricate costae.
Chapman, F. & Crespin, I. 1923. The Austral Rhynchonellacea of the “Nigricans Series,” with a special description of the new genus Tegulorhynchia. Proc. Roy. Soc. Vict., 35 (N.S.), pp. 170–93, Plates 11–13.
Hutton, F. W. 1905. Revision of Tertiary Brachiopoda of New Zealand. Trans. N.Z. Inst., 37 (June), pp. 474–81, Plates 45–6.
Thomson, J. A. 1915. Brachiopod Genera: The Position of Shells with Magaselliform Loops, and of Shells with Bouchardiform Beak Characters. Trans. N.Z. Inst., 47 (July 12), pp. 372–403.
—— 1918. (Brachiopoda of the Oamaru District). In J. Park, N.Z. Geol. Surv. Bull. No 20, pp. 117–119.
—— 1920. The Notocene Geology of the Middle Waipara and Weka Pass District, North Canterbury, New Zealand. Trans. N.Z. Inst., 52 (August 9), pp. 322–415, Plates 16–27.
—— 1927. Brachiopod Morphology and Genera. (Recent and Tertiary). N.Z. Board Sci. & Art, Man. No. 7, 338 pp., 103 figs., two plates.