212 REPORT UNITED STATES GEOLOGICAL SURVEY. 



12. YolseUa. (Braeliydontes) rcgularis White. 



Only fragments of this species were found at this locality, but they 

 seem certainly to be specifically identical with the type specimens from 

 the valley of Crow Creek, east of the Bocky Mountains, and also with 

 those that have been identified with them elsewhere west of the mount- 

 ains. It is described in the Bulletin of the United States Geological 

 and Geographical Survey of the Territories, vol. iv, p. 707. 



3. YolseUa (Braeliydontes) laticostata White. 



This species has been recognized at no other locality. It is described 

 in the same article with the preceding species. 



4. Nuculana inclara White. 



Peculiar interest is attached to this species, not only because it is the 

 first one of the genus and family to which it belongs that has been dis- 

 covered in the strata of the Laramie Group, but because the whole 

 family is regarded as a purely marine one ; while all the other species 

 yet discovered in this group, with perhaps the exception of Odontobasis, 

 are regarded as of either brackish or fresh water origin. Only two ex- 

 amples were found, but the condition of their preservation is such that 

 their generic identity is not doubted. It is described in the Bulletin 

 of the United States Geological and Geographical Survey of the Terri- 

 tories, vol. iv, p. 708, and it has been discovered at no other locality. 

 Its own characters, and being also associated with ~Ro. 10 of this list 

 (which is probably another marine form) near the base of the Laramie 

 Group, seem to- suggest that marine saltness of the waters was preserved 

 in some places for some time after the peculiar conditions of the Laramie 

 period were introduced. This suggestion is somewhat strengthened by 

 the fact that Odontobasis buccinoides White holds in the valley of Bitter 

 Creek a position considerably below the principal fossiliferous horizon 

 there, in which both fresh and brackish water forms are found, but none 

 whose living congeners are exclusively marine. It is a singular fact, 

 however, that in both these layers containing marine types specimens of 

 Melania were found ; but this subject will be discussed at some length on 

 subsequent pages. 



5. Corbicula cytheriformis Meek & Hayden. 



The specimens which I have referred to this species are imperfect, and 

 in the form of casts in the compact reddish shales which contain all the 

 fossils of this locality. A couple of the examples found here indicate a 

 larger size than any of those which have been identified with this species 

 from Bitter Creek Valley, but not larger than the types of Meek & Hay- 

 den. These were discovered by Dr. Hayden in the Judith Biver beds 

 of the Upper Missouri Biver region, and are figured and described in 

 vol. ix of the United States Geological Survey of the Territories. 



0. Corbicula ? 



These shales contain casts of another species of Corbicula which seems 

 to be different from any described form, but because those examples are 

 yet known only in the form of casts, and are probably not fully adult, 

 they are not specifically named. They resemble young examples of C. 

 jplanumbona Meek. 



7. Corbicula (LeptestliesJ/ractaMeek. 



Casts of this species were also found here, which are interesting as 

 showing that it began its existence early in the Laramie period. Here- 

 tofore it has been found only in the upper portion of the Laramie Group, 



