270 REPORT UNITED STATES GEOLOGICAL SURVEY. 



16: Exogyra ponderosa Eceiner. 



17. Exogyra tcxana Bceiner. 



18. Exogyra arictina Bcenier. 



19. JSpondylus 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 Ecemer.* 



21. Neithea duplicata Ecemer. 



22. Neithea texana Ecemer. 



23. Pinna . Undetermined species. 



24. Inoceramus deformis Meek ? 



25. Inoceramus . A large broad species. 



28. Lima . A robust spinulose species. 



27. Trigonia emoryi Conrad. 



28. Tapes Mlgardi Shumard. 



29. Protocardia texana Conrad. 



30. Arcopagia texana Ecemer. 



31. Anatina 1 . Undetermined species. 



32. Liopistha sancta-saba3 Ecemer sp. 



33. Gorymya . This species resembles an elongate Glycymeris, 



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

 which characterizes Gorymya. The collection contains only one 

 example, an internal cast. The species is undetermined. 



34. Pacliymya austinensis Shumard. 



35. Actosonella dolium Ecemer. 



36. Spiractceon . Undetermined species. 



37. Pleurotomaria f . The examples are rather large, and being 



imperfect their generic characters cannot be clearly determined, 

 but they appear to possess the general characteristics of Pleu- 

 rotomaria. 



38. Lunatia collina Conrad sp. 



39. Lunatia pedernalis Ecemer sp. 



40. Nautilus elegans Sowerby. 



41. Nautilus . Undetermined species. A cast only. 



42. Ammonites fiaccidicosta Ecemer. 



43. Ammonites leonensis Conrad. 



44. Ammonites peruvianus Von Buch. 



45. Placenticeras placenta DeKay. 



46. Turrilites brazosensis Ecemer. 



47. Serpula intrica White. 



48. Serpida . 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 



4| 



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

 attempt at rectification. 



