1874.] 243 [Rathbun. 



drab-colored limestone, containing fish remains and a few obscure 

 moulds of lamellibranchs. 



As I have not as yet had time to finish the study of all the nlol- 

 lusca collected on the Rio Maria Farinha, descriptions of only the 

 hxrger and more prominent forms among the lamellibranchs have 

 been given in this paper. In a future and more complete report I 

 hope to furnish figures of all the forms here described. 



Though disliking to increase the already large number of names 

 among the cretaceous moUusca, I have found it necessary to desio'- 

 nate and name as new all but two of the forms herein described. 

 They have been carefully compared with the collections in the Mu- 

 seum of Comparative Zoology at Cambridge, with those of the Boston 

 Society of Natural History, and also with the literature on the sub- 

 ject contained in the libraries of both the above-named institutions. 



I am greatly indebted to Mr. Alex. Agassiz, for kindly allowino-me 

 free use of the collection of Palseontology and the library in the Mu- 

 seum at Cambridge; and also to Count L. F. de Pourtales and Mr. 

 O. H. St. John of Cambridge, who aided me much in my compari- 

 sons. To Prof. A. Hyatt, of the Boston Soc. of Nat. History, I am 

 under many obligations for aid and advice in the prejiaration of this 

 short paper. It is due Mr. O. A. Derby of Cornell University, to 

 whom the first right of the collection belonged, to state here, that he 

 had already done some work upon it before I received it. He had 

 carefully prepared most of the specimens and separated many of the 

 species. The account of the localities is, of course, taken entirely 

 from his notes. 



Family OSTREID.E. 



Gryphaea (sp. ?) 



There are numerous internal moulds of a small oyster, belongino- to 

 this genus, but no external moulds perfect enough to show the true 

 specific characters of the form were obtained. The thickening with- 

 in the beak varies greatly, sometimes almost entirely filling up that 

 portion of the sheU. The exterior surface seems to have been 

 marked simply with small, irregular, concentric lines. From the cre- 

 taceous bed at Sao Jose, Prov. of PeriiamljucOj Brazil. 



Exogyra lateralis (Nilsson). 



Os'.rea lateralis Nils., 1827. Peti'if suocana. 



?? Chama canaliculaia Sow. 1813. Min. conch. 



There were obtained from the limestone bads at Siio Jose and Pt. 

 Nova Cruz two specimens of Ex:)gyra, which, with very little doubt, 



