WHITE.] LAEAMIE FOSSILS OF BITTER CREEK VALLEY. 219 



which were collected by Prof. E. D. Cope from the Judith Eiver beds of 

 the Upper IMissouii Elver rofiioii. It is described in Bull. U. S. Geol. 

 aud Geog'. Siu\ Terr. vol. iii, p. 000. 



15. JJnio danw Meek & Hayden? 



Several Avell-preserved examples were obtained with the other species 

 of Unio 5it Black Buttes Station that have much the form of the living 

 species U. rectus. They ai)pear, however, to be too neai-ly related to, if not 

 specilically identical with, U. dance Meek aud Hay den to warrant any other 

 reference at present. 



IC. Corhicula occidcnidlls Meek & Hayden. 



The possible identity of this species with the follo^\dng has already 

 been referred to, but the two forms although closely related are (when 

 studied by numerous specimens of each tbrm from Bitter Creek Valley) 

 quite readily distinguishable. The two forms are also from two separate 

 horizons, 0. occldentaUs being found only in that of Point of Eocks and 

 Black Buttes Stations, and G. cytheriformis only in that of the locahty 

 two miles below Point of Eocks. C. hannisteri Meek, as has akeady been 

 stated, is regarded as only a variety of C. occidentalis. This species is 

 quite abundant in the principal oyster layer at Point of Eocks, and is 

 similarly associated at the Yampa Yalley locaht5^ Among some collec- 

 tions brought by Professor Powell ii*om Upper Kanab, Utah, are some 

 examples that appear to belong to this species. It has not been recog- 

 nized east of the Eocky Mountains in Colorado. 



17. Corhicula cytheriformis Meek & Hayden. 



Many well-preserved examples of this species were obtained at the 

 locality two miles below Point of Eocks. They are of smaller average 

 size than the tj'pes of the species, but they seem to be specifically iden- 

 tical. This species was not recognized east of the Eocky Mountains in 

 Colorado, and only doubtfully so in the Danforth Hills, which is the only 

 other locality at which it has been recognized west of the Eocky Mount- 

 ains. 



18. Corhicula (Leptesthes) fracta Meek. 



A single layer at Black Buttes Station contains this species in great 

 abundance, and it was here and at Halhdle, four miles distant, that Mr. 

 Meek obtained the types of this species and of the subgenus Leptestlies. 

 Its geographical distribution is about the same as that of Melania loyomin- 

 gensis, and its vertical range apparently through the whole thickness of 

 the Laramie Group. For fm-ther remarks on this subject see notes on 

 the Laramie fossils of Crow Creek Valley. 



19. Corhula undifera Meek. 



The typical forms of this species have hitherto been found only at Eock 

 Springs and in the Danforth Hills. The tji^e collection of C. suhundifera 

 AVhitc was obtained at Point of Eocks station fi-om a laj'er about fifty 

 feet below the oyster horizon there, and the form was described in I'ro- 

 fessor Powell's Eeport on the Geology of the Uinta Mountains, p. 129, 

 The only other known examples were brought by Professor Powell fi'om 

 U])per Kanab, Southern Utah, as mentioned on a previous page. The 

 differences between these two forms are so slight that I am now disposed 

 to regard them as only varieties of one species ; but stiU the variation 

 seems to be constant as found in widely separated localities, which is 

 suggestive of a permanency that may prove to be specific. 



