270 REPOET UNITED STATES GEOLOGICAL SUEVEY. 



IG. Exogyra ponderosa Iiloemer. 



17. Exogyra texana Eoemer. 



18. Exogyra arietina Eoemer. 



19. Spondylus f . This is apparently a Spondylus. The few ex- 



amples of it in the collection are attached at full length to other 

 fossil shells. It is about two and a half centimeters long, and the 

 surface marked by numerous fine radiating lines. 



20. Modiola sancta sabce Eoemer.* 



21. N'eithea diiplicata Eoemer. 



22. JSfeithea texana Eoemer. 



23. Pinna . Undetermined species. 



24. Inoceranius deformis Meek ? 



25. Inoceramus . A large broad species. 



20. Lima . A robust spinulose species. 



27. Trigonia emoryi Conrad. 



28. Tapes MJgardi Shumard. 



29. Frotocardia texana Conrad. 



30. Arcopagia texana Eoemer. 



31. Anatina 1 . Undetermined species. 



32. Liopistha sancta-sdbm Eoemer sp. 



33. Corymya . This species resembles an elongate Glycymerisj 



but it has the internal rib radiating from the beak of each valve, 

 which characterizes Corymya. The collection contains only one 

 example, an internal cast. The species is undetermined. 



34. Paeliymya austinensis Shumard. 



35. Actceonella dolium Eoemer. 



36. Bpiractceon . Undetermined species. 



37. Fleurotomaria ? . The exjimijles are rather large, and being 



imperfect their generic characters cannot be clearly determined, 

 but they appear to possess the general characteristics of Fleu- 

 rotomaria. 



38. Lunatia collina Conrad sp. 



39. Lunatia pedernalis Eoemer sp. 



40. Wautilus elegans Sowerby. 



41. Nautilus . Undetermined species. A cast only. 



42. Ammonites flaccidicosta 'Rodm.&r. 



43. Ammonites leonensis Conrad. 



44. Ammonites peruvianus Von Buch. 



45. Flacenticeras placenta DeKay. 



46. Turrilites hrazosensis Eoemer. 



47. Serpula intrica White. 



48. Serpula . A large undetermined species. 



Taking a general view of the Cretaceous faunae of the different regions 

 of Western North America, we find that there is a marked difference 

 between certain of the widely separated regions. For example, the fauna 

 of the Texas region, including portions of the adjacent Territories ; that 

 of the Pacific coast, especially California, and that of the Upper Mis- 

 souri Eiver region, are each found to possess well-marked fanual pecu- 

 liarities. Not only are almost all the species in each region different 

 from those of any of the others, but several of the higher groups, as well 

 as peculiar types, are found to be restricted to each. The differences of 

 this character are as great, if not greater, between the Texas and Upper 

 Missouri Eiver regions as they are between either of these and that of 



*As a rule I adopt tlie nomenclature of tlie various authors in this list without any 

 attempt at rectification. 



