white.] LARAMIE FOSSILS OF BITTER CREEK VALLEY. 219 



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

 the Upper Missouri Biver region. It is described hi Bull. XJ. S. G-eol. 

 and Geog. Sur. Terr. vol. hi, p. 600. 



15. Unio dance Meek & Hay den"? 



Several well-preserved examples were obtained with the other species 

 of Un io at Black Buttes Station that have much the form of the living 

 species V. rectus. They appear, however, to be too nearly related to, if not 

 specifically identical with, U. dance Meek and Hay den to warrant any other 

 reference at present. 



16. Corbicula occidentalis Meek & Hayden. 



The possible identity of this species with the following has already 

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

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

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

 horizons, G. occidentalis being found only in that of Point of Bocks and 

 Black Buttes Stations, and C. cytlieriformis only in that of the locality 

 two miles below Point of Kocks. G. bannisteri Meek, as has already been 

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

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

 similarly associated at the Tampa Valley locality. Among some collec- 

 tions brought by Professor Powell from Upper Kanab, Utah, are some 

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

 nized east of the Bocky Mountains in Colorado. 



17. Corbicula cytlieriformis Meek & Hayden. 



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

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

 size than the types of the species, but they seem to be specifically iden- 

 tical. This species was not recognized east of the Bocky Mountains hi 

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

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

 ains. 



18. Corbicula (Leptesthes) fracta Meek. 



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

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

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

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

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

 the Baramie Group. For further remarks on this subject see notes on 

 the Baramie fossils of Crow Creek Valley. 



19. Corbula undifera Meek. 



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

 Springs and in the Danforth Hills. The type collection of C. silbundifera 

 White was obtained at Point of Bocks station from a layer about fifty 

 feet below the oyster horizon there, and the form was described in Pro- 

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

 The only other knowa examples were brought by Professor Powell from 

 Upper 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 still the variation 

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

 suggestive of a x>ermanency that may prove to be specific. 



