fact, compares more satisfactorily with some of the Cretaceous forms.

The comparison of Pecten rubidgeanus with P. subspinosus Schloth. cannot be pronounced at all fortunate, while we shall find that Lima obliquissima shows a closer agreement of characters with Cretaceous and later forms than with the European Jurassic shells cited by Tate.

Placunopsis subjurensis Tate, which was compared with P. jurensis Roem., may perhaps be an Anomia, and in some respects closely resembles A. pseudoradiata d'Orb., * from the Aptian. Placunopsis imbricata Tate is compared in the table with P. substriata Lyc., from the Oolites. P. semistriata (Bean) was probably the English shell with which it was intended to institute comparison, since this name alone is mentioned in Tate's description on page 154 of his paper. P. imbricata, however, is without radial ornamentation, but is characterised by well-spaced concentric ridges which recall the similar ornamentation of Anomia neocomiensis d'Orb., † though occurring in less emphasised form. The illustration of P. imbricata gives a very poor idea of the shell, but an examination of the specimen dispels the notion of a close comparison with known Jurassic forms.

Trigonia cassiope Tate is not to be united with any known Jurassic costate Trigonia, and was accordingly renamed T. tatei by Neumayr. It is well distinguished by the elongated escutcheon, the very delicate marginal carina, and the fine character of the ornamentation on the area and escutcheon. Trigonia goldfussi Tate is an immature shell, and in all probability illustrates the youthful stage of one of the large and robustly ornamented Pseudo-quadrate which form such a striking feature in the Uitenhage fauna. It certainly does not represent either Trigonia goldfussi Agassiz or T. painei Lyc. (=T. goldfussi Morr. and Lyc.), with which it was identified. Tate himself, on page 159 of his paper, said: "Hereafter, however, it may be found to be the young of a distinct species." It is therefore the more regrettable that the error of quoting this European Jurassic shell from the Uitenhage beds should have continued to be perpetrated. Stow repeatedly used the name "T. goldfussi" in his paper, but I have been unable to ascertain to which of the Trigoniæ he referred.

No importance can be attached to the comparison of such types as

*

d'Orbigny (4), p. 84; Woods (3), vol. i., p. 27, pl. v., figs. 1-3 (1899).

† d'Orbigny (3), p. 754, pl. 489, figs. 1-3 (1848).

Stow (1), pp. 497-514.

Pinna atherstoni Sharpe and P. sharpei Tate with Jurassic forms, for it is evident that these representatives of the genus lack any strong distinctive characters which alone would render them of value in an estimate of geological age.

Mytilus baini Sharpe was compared with M. sowerbianus d'Orb., from the Oolites of Europe. It is a Modiola which certainly has characters of form and ornamentation closely similar to those which distinguished M. sowerbiana (d'Orb.) and M. perplicata (Etallon); but this type of Modiola is by no means confined to Jurassic rocks, having also a widely distributed representative in the Cretaceous M. flagellifera (Forbes), to mention a well-known example.

Pholadomya dominicalis Sharpe was thought to resemble Liassic and Oxfordian forms, but it may equally well be brought into comparison with Lower Cretaceous representatives; for example, the European Aptian shell ascribed, rightly or wrongly, to P. pedernalis Roem.*

Astarte pinchiniana Tate was brought into comparison with A. pumila Goldf. and A. excentrica Morr. and Lyc., from the Great Oolite of Europe. The African shell differs in important respects from these, and, as will be pointed out below, it probably belongs to the sub-generic group Eriphyla and is certainly most closely comparable with Cretaceous forms.

Berenicea antipodum Tate was believed by Tate to be related to B. striata Haime, from the Lower Lias of France, but has been regarded by Prof. J. W. Gregory † as a close ally of the Cretaceous B. gracilis (Milne Edwards).

Two Uitenhage Serpula were identified by Tate with S. filaria Goldf. and S. plicatilis Münst., from the Inferior Oolite of Europe. The specimens ascribed to S. plicatilis represent an adherent form sharply carinated on the back, with a weaker carinal angle on either side and a circular aperture, but the true S. plicatilis Goldf. has only a single central, longitudinal keel. S. quinquangularis Goldf. ‡ (Upper Jurassic) stands much closer in its characters, and a Serpula scarcely distinguishable from this occurs in the Lower Cretaceous of Europe, and may be found named S. quinquangularis in some collections. S. filaria Goldf. is a solitary, wholly adherent form, commencing with a coiled stage. So far as can be seen from the imperfect African specimen named S. filaria by Tate, this is a clustering form consisting of crowded, narrow cylindrical tubes, and * Pictet and Renevier (1), p. 60, pl. vi., fig. 7, 1855; Moesch (1), p. 93, pl. xxxiii., fig. 2. + Gregory (1), p. 112. Goldfuss (1), Band i., p. 230, pl. 68, fig. 8 (1831).

it is not distinguishable from the English Lower Cretaceous Serpulæ that have been variously referred to Serpula filiformis J. de C. Sow, and S. plexus J. de C. Sow. We thus see that in the case of the two Trigonia and the two Serpula which Tate identified with European Jurassic types, the determinations were so far erroneous that they are now bereft of the significance which was attached to them as evidence for the age of the fauna.

We may further examine the evidence for age afforded by some of the more conspicuous bivalves, and firstly I may briefly refer to the representatives of the genus Trigonia, which in themselves lend such a characteristic aspect to the fauna. Although the testimony of these is perhaps not quite so conclusive as Lycett supposed, still, the balance of evidence furnished by members of this genus may be safely relied upon to give a fair indication of age, even when considered apart from associated forms, and the material we are dealing with in the present instance is fortunately of an exceptionally favourable character. In the first place there is Trigonia ventricosa, T. kraussi, and T. rogersi, all possessing the characters of the section Scabræ a division which, so far as we know, is elsewhere only represented in rocks of Cretaceous age. These might be considered to be balanced by the occurrence of T. tatei, a typical member of the section Costatæ, but although this division of the Trigoniæ has its maximum development in the Oolitic rocks, it is also represented in strata of Lower Cretaceous and even later age.

Trigonia peninsularis Coquand,* from the Aptian of Spain, certainly shows characters of degeneration not shared by T. tatei, but the Oomia strata of Cutch have yielded two normal representatives of the Costatæ, which, together with some degenerate derivatives of this section, are accompanied by Trigonia which exhibit a decidedly Cretaceous aspect. Another unmodified costate form, T. angustecostata Behr. t occurs in the Argentine Republic in strata which are regarded by Behrendsen as Upper Cretaceous, while a typical member of this section has been described by E. Ascher from the Grodischter beds (Hauterivian) of Silesia. ‡

Trigonia herzogi (Goldf.), another very characteristic Uitenhage form, was believed by Lycett to belong to the Quadratæ, which, so far as known, are exclusively Cretaceous. Steinmann, § however, pointed out that Trigonia herzogi differs in several important par

Coquand (1), p. 129, pl. xxiii., fig. 3.

Behrendsen (1), p. 6, pl. 3, fig. 7.

Ascher (1), p. 159 [25], p. xiii. [ii.], fig. 10. § Steinmann (2).

ticulars from all known Quadratæ, and found that the special features which distinguish this Uitenhage shell from the Jurassic Clavellatæ on the one hand and the Cretaceous Quadratæ on the other, are shared by Trigonia transitoria Steinm. from Lower Cretaceous rocks in Bolivia, Chili, and the Argentine Republic. He therefore suggested a new group-name, the Pseudo-quadratæ, to comprise these two Trigonia, which were the only examples known to exhibit these. peculiar distinguishing characters. Trigonia neuquensis Burckhardt,* which occurs with T. transitoria in Neocomian rocks at Las Lajas on the Rio Agrio (Argentine), falls under the same heading, while T. mamillatat from the Oomia strata in Cutch must also be referred to this group. Still another form, described in these pages (T. holubi), is clearly referable to the same category. Although the five members of the Pseudo-quadratæ known to us are all similarly differentiated from the typical Clavellatæ, it is not certain that they are all so closely related to one another as might at first sight appear to be the case; some, at least, may possibly have been independently evolved from clavellate ancestors. Nor is it by any means certain that they bear any close and direct relationship to the true Quadratæ, and though definite indications on this point fail us, it is quite probable that the Quadratæ and Pseudo-quadratæ represent parallel and independent groups of derivatives arising from Jurassic Clavellatæ. It is therefore evident that the Trigonia of the group Pseudoquadratæ caunot yet be considered in themselves to furnish quite such reliable guidance to geological age as the true Quadratæ, but at the same time their general aspect, by comparison with the Quadratæ, strongly suggests a Cretaceous age, while the known South American representatives must, in fact, be regarded as Neocomian. Some of the most important features wherein the Quadratæ differ from the Clavellatæ are also exemplified in the Pseudo-quadratæ. Lycett laid great emphasis on the presence or absence of sculpture on the escutcheon in distinguishing between the Jurassic Clavellatæ on the one hand, and the Cretaceous Clavellatæ and Quadratæ on the other, and in regard to this feature all the Pseudo-quadratæ agree with the Quadratæ in having coarsely nodose ornamentation on the escutcheon. Further remarks on the points of agreement between these groups are appended to the description of Trigonia holubi.

Trigonia conocardiiformis (Krauss) was thought by Lycett to fall

* Burckhardt (2), p. 74, Taf. xiv., figs. 4-6.

Kitchin (1), p. 100, pl. ix., figs. 8, 9; pl. x., figs. 1–3.

Remarks on this subject will be found to follow the description and the discussion of the relationships of Trigonia holubi, in these pages.

within the section Scabræ, but a near relationship to members of this division is scarcely to be inferred from the adult characters displayed by this peculiar form, while a study of the young shell does not plainly reveal its affinities. A general comparison, however, shows that this Trigonia differs from the Jurassic Clavellatæ in a manner somewhat analogous to that which distinguishes the Scabræ, and a very closely similar and probably intimately related form occurs in the Neocomian of the Argentine Republic.

On the whole, so far as this Trigonia-assemblage is comparable with European forms, it must certainly be considered to display a Cretaceous rather than a Jurassic character, though when regarded collectively, it is without counterpart in the European area. The significance of other Trigonia included in this fauna will be discussed presently.

Still further indications of geological age are to be derived from a comparison of the Uitenhage lamellibranchs with European types. One of the shells submitted to me, which proves to be identical with a form previously described by Sharpe, who did not recognise its true generic position, is an example of the well-characterised genus Thetironia, which in Europe is widely distributed in Lower Cretaceous and higher strata, though it has not been recorded from rocks of an earlier age. A second species of Thetironia is also included in the collection. Solecurtus is another genus not known to occur in rocks older than Cretaceous, and a representative of this must now be added to the list of Uitenhage molluscs. The specimens sent to me for examination also include examples of Pecten which can only be identified with the Cretaceous P. orbicularis J. Sow. and P. cottaldinus d'Orb., while a third form may be most aptly brought into comparison with P. subacutus Lam. A representative of the Cretaceous genus Anthonya must also be recorded in this connection.

Gervillia dentata Krauss, though belonging to the group of G. aviculoides, typically represented in Jurassic rocks (G. deecki Frech; G. aviculoides Sow.), has a close counterpart in G. anceps Desh. and G. sublanceolata d'Orb., in the Lower Cretaceous of Europe. A form closely similar, and perhaps identical, occurs also in the Neocomian of German East Africa. The long lateral tooth which Krauss thought to be so highly distinctive of G. dentata as almost to justify the establishment of a new genus, is a normal feature of the group, and is well developed in G. anceps. Another common

* Frech (1).

Frech (1), pp. 612, 613.