36 Annals of the South African Museum. 



within the section Scabrae, 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, how- 

 ever, shows that this Trigonia differs from the Jurassic Clavellatse 

 in a manner somewhat analogous to that which distinguishes the 

 Scabrae, and a very closely similar and probably intimately related 

 form occurs in the Neocomian of the Argentine Kepublic. 



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 speci- 

 mens 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 repre- 

 sentative 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 

 Freeh ; 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. f Another common 



* Freeh (1). f Freeh (1), pp. 612, 613. 



r 



