white.] LARAMIE FOSSILS OF BITTER CREEK VALLEY. 221 



the Laramie Group. Mr. Meek obtained his type specimens at the Black 

 But tes locality, and it has since been obtained in considerable numbers 

 both east and west of the Bocky Mountains, in Colorado and Wyoming, 

 but it has not yet been discovered in the Upper Missouri Biver region. 

 Its wide geographical distribution ; its great vertical range in the Lara- 

 mie Group ; its apparently true Melanian type and its relation to the fol- 

 lowing species from a lower horizon in the group in Bitter Creek Valley, 

 all make it a species of unusual interest. For further remarks on it 

 see notes on Laramie fossils from Crow Creek Valley and the Danforth 

 Hills localities. 



26. Melania insculpta Meek. 



Mr. Meek described this species in the Ann. Beport of the U. S. Geol. 

 and Geog. Sur. Terr, for 1872, p. 515, along with M. wyomingensis, his 

 types of the former having been obtained at Bock Springs, and those of 

 the latter at Black Buttes Station. IsTo examples of M. insculpta have 

 been found elsewhere than at Bock Springs, except two or three imper- 

 fect ones at the locality two miles below Boint of Bocks. It is much 

 more nearly related to M. wyomingensis than would appear at first glance, 

 because the principal difference consists in the row of prominent nodes 

 or short spines that adorn the larger volutions of the latter ; while the 

 upper turns of the spine of each seem to be indistinguishable. This is 

 another case of very closely related species or well-marked varieties 

 existing the one above and the other below the line of unconformity that 

 has been shown to exist in the Laramie strata of Bitter Creek Valley. 



27. Viviparus plicapressus White. 



The only localities at which this species has yet been discovered are 

 those of Black Buttes Station and Tampa Valley. At the latter locality 

 it was found associated with Melania wyomingensis and JSferitina volvili- 

 neata :■; and at the former with Unio, Gorbula, Goniobasis, Gassiopella, 

 Campeloma, &c. It is described in Bo well's Beport on the Geology of the 

 Uinta Mountains, p. 133. It is not yet known east of the Bocky Mount- 

 ains. 



28. Tulotoma thompsoni White. 



Black Buttes Station is the first locality at which this species was dis- 

 covered, and the valley of Crow Creek, east of the mountains, is the only 

 other one at which it has been found. It occurs in considerable numbers 

 at each of these localities, and its identity at each is beyond question. 

 Its associates at Crow Creek are all fresh-water forms ; and at Black 

 Buttes it seems to occupy a thin layer by itself between those which con- 

 tain both brackish- and fresh-water forms. See further remarks under 

 the head of "JSotes on the Laramie fossils of Crow Creek Valley." 



29. Gampeloma vetula Meek & Hayden. 



Dr. Hayden first discovered this species in the Judith Biver beds of 

 the Upper Missouri Biver region, and it is described and figured in volume 

 IX of the United States Geological Survey of the Territories. A goodly 

 number of examples were obtained at Black Buttes Station, where they 

 were found associated with Unio, Corbula, Goniobasis, Gassiopella, &c. 

 Their specific identity with Gampeloma vetula seems to be unmistakable. 



30. Gampeloma multistriata Meek & Hayden. 



Some examples found associated with the foregoing species at Black 

 Buttes Station possess distinct revolving lines like those of G. multistriata, 

 but they lack the shouldering of the distal side of the body- volution so 

 common in that species. As they do not appear to differ materially in 



