Genus Notostrea Finlay, 1928.
Type: Ostrea subdentata Suter.
Notostrea tarda (Hutton). (Figs. 86–96.) 1873. Gryphea tarda, Hutton, Cat. Tert. Moll., p. 35. 1914. Gryphea tarda, Hutton: Suter, N.Z. Geol. Surv. Pal. Bull. 2, p. 47, pl. 13, figs. 1a, b.
Localities: Bryozoan limestone, Tioriori; limestone boulders at head of Whangamoe Inlet (wrongly named Whangatete on L. and S. map, 1910); base of tuffaceous limestone, Waikaripi.
Many specimens were collected at what is probably the type locality at Tioriori where they occur in great numbers. The speci-
mens figured are not exceptional ones, but give a fair idea of the great range in width and incurving. The writer is indebted to Dr. H. J. Finlay for drawing his attention to the close relationship between Gryphaea tarda and Ostrea subdentata Suter, and for questioning the use of Gryphaea for Hutton's species. Trueman (1922, p. 264) writing on Gryphaea of the Lower Lias, had previously pointed out that this genus is based on form alone and does not represent a genetic line. He says, “It is extremely likely that these gryphaeiform shells have been evolved repeatedly during the Jurassic and Cretaceous from species of Ostrea that are similar and are presumably closely related. In other words ‘Gryphaea’ is a polyphyletic group, containing species evolved along many different lines. Therefore, the name Gryphaea can only be applied strictly to one of these series, and each such series should receive a separate generic name; but until more of their characteristics are known, at least, it appears undesirable to add to the existing confusion by creating new names for each group.” This objection does not apply to the Tertiary Notostrea of Finlay which is not likely, in New Zealand, to be confused with any other “Gryphaea,” for none of these shells have been found in the Mesozoic of this country. However, the question of whether the South American and South Australian Tertiary examples should be classed as Notostrea arises. It seems likely that they also have arisen each independently in their own seas and do not indicate genetic connection.
The writer formerly thought (Ferrar, 1925, p. 295) that the posterior position of the adductor muscle, and the well-developed posterior lobe with its bounding groove showed relationship between “Gryphaea” tarda and the Jurassic G. arcuata Lam., but had to change his opinion after seeing some specimens of Ostrea charlottae Finlay from Castlecliff. These have the typical sculpture of ordinary charlottae but in shape, size, and other features agree with the moderately-curved specimens of tarda. The right valve is correspondingly modified and is extremely like the one figured below (Figs. 94–96).
It may be mentioned in passing that, following Fisher. Cossman (1914, p. 389) gives the recent G. angulata Lamarck as the type of Gryphaea, and recognizes Liogryphaea Fischer, founded on the Jurassic G. arcuata Lam. Dall, however (1898, p. 673) had previously shown that when Gryphaea was introduced in 1801, G. angulata was a nomen nudum and therefore without status. He argued rightly that the type must be chosen from the valid species of Lamarck's original list and named G. arcuata Lam. as genotype. Liogryphaea Fischer is therefore an absolute synonym of Gryphaea Lamarck.