The Invertebrate Fauna of the Uitenhage Series. 49 



Some indications of a western extension of the same type of fauna 

 are to be recognised on the South American continent. 



(e) Neocomian in South America. Amongst the fossils collected 

 in 1899 by the late J. B. Hatcher from the Pueyrrydon Series in 

 Patagonia" are several lamellibranchs of distinctive type which 

 permit of close comparison with some of those above discussed. 

 They have been described and figured by Stanton,! who was led 

 to ascribe a Lower Cretaceous age to the Pueyrrydon Series, though 

 he was unable to establish a narrower correlation with the forma- 

 tions of other regions. The most striking resemblances to Uitenhage 

 forms are seen in two Trigonia from the Belgrano beds, T. sub- 

 rentricosa Stanton, a member of the section Scabrae, and T. hetero- 

 sculpta Stanton, believed by Stanton to be allied to T. vau Sharpe. 

 Trigonia subventricosa certainly approaches very closely to T. ven- 

 tricosa, particularly in the wide spacing and robustness of the 

 anterior varices. The differences in the sculpture pointed out by 

 Dr. Stanton appear to be less emphasised when this Patagonian 

 form is brought into comparison with the large and more coarsely 

 ornamented T. kraussi sp. nov., which occurs with T. ventricosa. But 

 if the relations of height to length exhibited by the figured specimen 

 of T. subventricosa be those which characterise the average shells 

 of that form, then there is good ground for the separation of these 

 three members of the Scabrae, which at the same time appear to be 

 united by similar broad features of peculiar form and ornament. 

 They are the only known examples of this particular extreme type, 

 and probably represent a group in this southern developmen 

 parallel with that of which T. scabricola Lycett and T. aliformis 

 Park, are typical members in Europe. 



The ornamentation of T. heterosculpta is of such a kind as to 

 recall instantly the conspicuous shells of the groups of T. v-scripta 

 and T. vau. The principal points of resemblance are the manner in 

 which steeply inclined ribs of two series on the flank meet to form 

 an angular pattern, and the absence of sculpture from the area and 

 the posterior portion of the flank in the adult shell. T. heterosculpta 

 is certainly not to be brought into comparison with the European 

 Undulatae, but its whole aspect suggests a close connection with the 

 group of T. vau. Its near relationship to T. vau and T. stowi is 

 clearly to be inferred from a comparison of the youthful characters, 

 which are very similar, and affinity with these rather than with the 

 Indian group of T. v-scripta is exactly what we might expect to 

 find, having regard to the geographical relationships. The adult 

 * Hatcher (1). t Stanton (3). 



