NOTES ON SOME 



MEXICAN CRETACEOUS FOSSILS, 



WITH DESCRIPTIONS OF NEW SPECIES. 



The following fossils were collected by my lamented friend, 

 Remond, several years ago, in the Sierra de las Conchas, near 

 Arivechi, Sonora. When they were first received, I published 

 a short notice of them, in the Proceedings of the California 

 Academy of Natural Sciences, accompanied by some extracts 

 from M. Remond's letter, and mentioned the close relationship 

 that obviously exists between this deposit and the Cretaceous of 

 Texas ; at the same time giving a list of the species identified, 

 in hastily glancing over the collection. Although sufficiently 

 accurate for the purpose, the list contained one or two errors in 

 identification of species, due to the imperfect character of some 

 of the specimens, in the first instalment received. In the present 

 paper I have endeavored to correct the errors, and believe that I 

 have correctly determined all the previously known species. 



The occurrence of the Texan Cretaceous fauna on the western 

 face of the Sierra Madre, is a matter of great interest, since it 

 proves conclusively that during that era there must have been a 

 water communication between the great Cretaceous sea, that 

 covered so much of what is now the central portions of our con- 

 tinent, on the one side, and the Pacific on the other. It is the 

 more remarkable when taken in connection with the fact, that of 

 the more than three hundred species now known in the Califor- 

 nian Cretaceous, barely one per cent, is found in common on the 

 two sides of the continent. From the occurrence in California 

 of Gryphcea vesicularis and Turritella senatim-granulata, determined 



pal. vol. ii.— 34 ( 257 ) 



