STANTON : THE MARINE CRETACEOUS INVERTEBRATES. 



Trigonia subventricosa, 

 Astarte peralta, 

 Astarte postsulcata, 



Hatchcriceras (?) tardense, 

 Hatchericeras (?) pueyrrydonense. 



Nine of these species together with a number of additional ones were 

 obtained at the other locality in the Belgrano beds ten miles east of 'Lake 

 Peuyrrydon. It is evident from an examination of the fossils that the 

 collections from these two localities supplement each other and are from 

 practically the same horizon as Mr. Hatcher determined in the field. 

 The list of species from the second locality is as follows : 



Pecten (Camptonectes) pueyrry- 



donensis, 



Pecten argentinus, 

 Pecten octoplicatus, 

 Mytilus (?) argentinus, 

 Pinna sp., 



Nucula pueyrrydonensis, 

 Trigonia subventricosa, 

 Trigonia heterosculpta, 

 Trigonia, sp., 

 Astarte postsulcata (?), 

 Tapes (?) patagonica, 

 Tapes (?) sp., 



Tellina sp., 



Solecurtus (?) limatus, 

 -Mactra (?) sp., 

 Corbula crassatelloides, 

 Dentalium (Laevidentalium) lima- 



tum, 



Vanikoro (?) sp., 

 Lunatia constricta, 

 Aporrhais patagonica, 

 Cinulia australis, 

 Tornatellaea patagonica, 

 Hatchericeras argentinense. 



Combining the collections from both localities, the Belgrano beds have 

 yielded 36 species of invertebrates that are more or less fully described 

 in the following pages, besides several additional forms represented by 

 material too scanty and imperfect for generic identification. 



Although the specific names in the above lists are all new, the assem- 

 blage of genera at once proclaims their Mesozoic character, and the ap- 

 pended excellent illustrations, drawn by Dr. J. C. McConnell, give 

 abundant proof of their Cretaceous age. 



The exact position of the beds yielding them in the Cretaceous system, 

 as developed in Europe and other parts of the world, is more difficult to 

 determine, because the evidence is incomplete and somewhat conflicting. 

 Perhaps the first question to suggest itself is whether more than one 

 great subdivision of the Cretaceous is represented in the three fossiliferous 



