The Invertebrate Fauna of the Uitenhage Series. 51 



herzogi. Dr. Stanton has suggested that a Trigonia quoted by 

 Behrendsen* as " Trigonia cf. aliformis Park." from supposed Upper 

 Neocomian beds at the Arroyo Pequenco may possibly be identical 

 with the Patagonian T. subventricosa. It is accompanied by an 

 oyster which Behrendsen identified with Exogyra couloni, and found 

 to agree well with the figures of Ostrea couloni cited by Bayle and 

 Coquandf from the Neocomian at Arqueros in Chili. The Chilian 

 shells ascribed to 0. couloni bear a considerable resemblance to the 

 Uitenhage Exogyra imbricata Krauss, with which Coquand even later 

 identified them,! and accompanying this oyster in Chili is Trigonia 

 delafossei Bayle and Coquand, the resemblance of which to T. ven- 

 tricosa has been elsewhere remarked upon. Associated with these 

 forms is a Crioceras identified by Bayle and Coquand with the 

 European C. duvali Le>., thus recalling the analogous association 

 of Trigonia ventricosa, Crioceras spinosissimum and Exogyra imbri- 

 cata in South Africa. Of the above-mentioned Mollusca, Trigonia 

 delafossei, T. transitoria, T. neuquensis> and T. cf. conocardiiformis 

 suggest very strongly their relationship to Uitenhage and Oomia 

 forms. It should be noted also that Philippi has described Trigonia 

 from localities in Chili, which share the characters of peculiar 

 sculpture and siphonal elongation shown by the group of T. vau 

 Sharpe, while T. eximia E. A. Philippi, from the Tinguirica valley 

 in Chili, appears to be closely related to T. conocardiiformis (Krauss) 

 and Burckhardt's T. cf. conocardiiformis. 



IV. THE DISTEIBUTION OF THE UITENHAGE FAUNA 

 IN EELATION TO SOME THEOEETICAL QUESTIONS. 



We may now briefly -consider in what measure the correlation 

 of the Uitenhage Neocomian fauna with the similar assemblages in 

 German East Africa and in Cutch bears upon the theory of an Indo- 

 African land barrier during early Cretaceous times ; and further, we 

 may inquire how far the facts concerning the dispersal of these 

 Mollusca have significance in relation to Neumayr's theory of distri- 

 bution according to climatic zones, as deduced from a study of the 

 Cephalopoda. The one question is in reality largely bound up with 

 the other, and since in both cases the inquiry is of a so purely 

 palseontological character, it may be of advantage briefly to review 

 the evidence now available. Moreover, it is advisable to glance at 



* Behrendsen (1), p. 418. t Bayle and Coquand (1), p. 37. 



+ Coquand (2), p. 158. 



Lycett (3), p. 120 (1875) ; Kitchin (1), p. 108 ; Paulcke (1), p. 296. 



