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. mamillata † 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 Quadrata 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 cannot 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 Quadrata 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

and characteristic Uitenhage shell is Exogyra imbricata Krauss, and this belongs to a general type well exemplified in the Lower Cretaceous strata of Europe and South America. Lima neglecta Tate, belongs to the sub-generic division Mantellum, and most closely resembles forms which occur in the Lower Cretaceous of Europe. Reference has already been made to Ptychomya complicata (Tate), which is a typical representative of a genus widely distributed in the Lower Cretaceous rocks, where it first makes its appearance.

It is abundantly evident, then, that many of the most important and distinctive molluscan forms, amongst those with which we are dealing, give similar indications of geological horizon. There can be no doubt, indeed, that the marine Uitenhage fauna is of Neocomian age, though it is perhaps not possible to arrive at a very precise and positive estimate of equivalence with the divisions of the Neocomian in Europe, owing to the want of close coincidence in the faunas as developed in such widely separated regions. But Holcostephanus atherstoni (Sharpe) and H. wilmanæ sp. nov., if not actually represented in Europe, have very close allies there in the Valanginian and Hauterivian, and the Uitenhage Marine Beds may, in my opinion, be certainly correlated with these divisions. Further, it seems to me highly probable that the Marine Beds represent not more than the strata at the top of the Valanginian and the base of the Hauterivian.

The possibility that the lowest marine strata may be of greater age than Neocomian is not only most remote, but is contradicted by the paleontological evidence, so far as this goes. Fossiliferous strata, yielding a marine molluscan fauna characterised by the prevalence of Gasteropoda and the remains of oysters, occur at Dunbrodie (Sunday's River) associated with plant-bearing beds, and are in the lower part of the Uitenhage Series; according to Messrs. Rogers and Schwarz they may be classed with the so-called "Wood Bed series. Amongst the fossils collected here are Actæonina atherstoni (Sharpe), Cyprina rugulosa Sharpe, and a Pecten which I have identified as Pecten cottaldinus d'Orb. While Acteonina atherstoni is found also in the highest part of the Marine Beds on the Zwartkop's River and with the characteristic Trigonia on the Sunday's River, Stow recorded the occurrence of Cyprina rugulosa with similar associates. Although the Wood Bed series was not seen in the Zwartkop's River Valley below Uitenhage, the lowest part of the Marine Beds in the Zwartkop's River section, exposed in a clay-pit near Rawson Bridge, yielded Acteonina atherstoni and

shells most probably referable to Bochianites glaber sp. nov.; the latter has close affinities with European Neocomian forms and occurs at a higher level in the Marine Beds one mile from Rawson Bridge on the main line, up side. It is also worthy of remark that the lowest marine strata found, either at Dunbrodie or in the Zwartkop's River Valley, yielded no single form which suggests stronger affinities to Upper Jurassic than to Lower Cretaceous types; but those very forms, such as Trigonia tatei Neum. or Tancredia schwarzi sp. nov., which if considered alone might with some reason have been thought to point to a Jurassic age, occur in the higher part of the Marine Beds, associated with characteristic Mollusca of undoubted Neocomian type.

During his visit to the Sunday's River district in 1905, Mr. Rogers found additional evidence to show that the whole of the Uitenhage beds there exposed were deposited with comparatively great rapidity. He found that forms which are represented in the strata by abundant individuals occur much more generally distributed throughout the whole thickness of beds than was at first suspected. Some of the most typical species of the marine facies (for instance, the familiar Trigonia) were observed to occur, together with layers of lignite, at the very base of the Sunday's River Beds, where Mr. Rogers had expected to find forms characteristic of the Wood Bed facies. These marine forms occur also 300 feet higher in the series, and since the lower beds of the series were seen to be assuming, in some degree, the aspect of the Wood Bed development, the discovery of the familiar marine forms in them occasioned some surprise. Mr. Rogers noted the occurrence of Hamites near the mouth of the river, where Stow obtained it at first, but he also found it high up the river in a rock which showed resemblance to the strata of the Wood Bed series. He concludes from his observations during this second survey, that Stow must have been led through insufficient collecting to assign a too restricted vertical distribution to various species. Mr. Rogers believes that from the same cause his own records are likely to prove faulty, and that exhaustive collecting would still more fully demonstrate the extensive vertical distribution of many of the forms throughout the beds exposed.*

The above considerations lend great support to the results of a comparative study of the fauna, namely, that no forms are known to occur in these beds which give definite indications of the presence of more than the equivalent of a single palæontological stage. Allowing, then, that the cephalopods, supported in no small degree * For the published account of the 1905 survey, consult Rogers (2), pp. 15–33.

by the lamellibranchs, afford satisfactory data for a comparison with European standards, we may safely conclude that no portion of the Uitenhage Series represents a period of time earlier or later than the Neocomian. It must be said, indeed, that the almost entire restriction of Holcostephanus, sensu stricto (= Astieria Auctorum), to the upper part of the Valanginian and lower beds of the Hauterivian in Europe suggests much narrower limits, when we consider how important a place is taken by members of this genus in characterising the cephalopod-fauna of the Uitenhage beds.

*

Leaving, now, the consideration of evidence which leads to these conclusions, we may proceed to compare the Uitenhage fauna with those occurrences in extra-European regions which, in greater or less degree, bear the imprint of a similar facies.

III.-COMPARISON WITH EXTRA-EUROPEAN FAUNAS. (a) Possible Traces of a Related Fauna in the South-west of Madagascar.-Douvillé has drawn attention to the occurrence of some lamellibranchs obtained by Lieutenant Boutonnet from deposits situated in the Fiherenga Valley, in the basin of the Isakondry River, east of Tullear. Mention is made of a large Trigonia, said to be analogous to some of the Trigonia of the Oomia beds in Cutch and of the Uitenhage Series, and with this is associated a shell referred by Douvillé to the genus Pycnodonta, and said by him to be closely comparable with Exogyra imbricata Krauss (also referred to Pycnodonta by Prof. Douvillé). On the evidence of these fossils, the strata containing them are considered by Douvillė to be of Cretaceous age, and Lemoine classes them provisionally as Lower Cretaceous. The account of these fossils so far published is unfortunately meagre, and it must here suffice to have drawn attention to the occurrence of forms in Madagascar which may possibly indicate the presence of a fauna of Uitenhage character.

(b) Comparison with the Fauna of the Oomia Group in Cutch.Striking data for correlation are to be found among the lamellibranchs which constitute so large a part of the Uitenhage fauna, and it becomes apparent that some of the conspicuous elements which help to lend a definite character to the assemblage, while finding no exact parallel in the European area, have an unmistakable counterpart in the fauna of the Oomia Trigonia-beds. This * In North Germany, for instance, the restriction of these forms to such narrow limits is well marked. See von Koenen (3), pp. 4, 8, 9.

† Douvillé (2), p. 388; Douvillé (4), p. 215; Lemoine (1), p. 176.