Mesozoic and Coiuozoic Geology and Palceontoloyy. 263 



Prof. 0. C. Marsh* described, from the Mioceue of the Rocky moun- 

 tain region, Moropus distaas, 31. senex, and Allomys nitens; from the 

 Green River Group of Wyoming, Heliobatus radians; and from the 

 Pliocene of the Rocky mountains, Moropus elatus, Tapiravus rarusi 

 Bison ferox, B. alleni, and C'rocodilus Solaris. 



Prof. F. B. Meekf described, from the Miocene at Cache valle3% Utah? 

 Limna^a kingi. 



Dr. C. A. White]; described, from the Wasatch Group at Bhxck Buttes 

 Station, W^'omiug, Unio provitus, U. holmesanus, U. endlichi, U. 

 couesi ; and from Wales, in Utah, and the Canon of Desolation, of 

 Green river, Unio mendax ; from the Tertiary,§ at Last Bluff, Utah, 

 Fhysa pleuromatis ; and from Joe's Valley, Viviparus ionicus. 



In 1878, Prof. C. A. White|| said the Wasatch Group is the lowest of 

 a series of three fresh-water Tertiary Groups, all of which are inti- 

 mately connected, not only by an evident continuity of sedimentation 

 throughout, but also by the jjassage of a portion of the molluscan 

 species from one group up into the next above. Not only were these 

 three groups, aggregating more than a mile in thickness, evidentlj^ 

 produced by uninterrupted sedimentation, but it seems equally evident 

 that it was likewise uninterrupted between the Laramie and Wasatch 

 epochs, although there was then a change from brackish to fresh 

 waters, and a consequent change of all the species of invertebrates 

 then inhabiting those waters. 



The Wasatch Group, for which " Vermilion Creek Group" and 

 "Bitter Creek Group" are uncalled-for synonyms, in the Green river 

 region, consists very largely of soft, variegated bad-land sandstones, 

 that reach a thickness of about 1,500 feet, together with from 100 to 

 300 feet of the ordinary indurated sandstones, alternating with bad- 

 land material at the base, and a similar amount of similar material at 

 top, the estimated aggregate thickness being about 2,000 feet. 



Resting immediately and conformably upon the Wasatch are the 

 strata of the Green River Group. Although intimately connected with 

 the former by continuous sedimentation and specific identity of mol- 

 luscan species, they differ considerably from those of that group in 

 general aspect, and in composition also. The group is lithologically 



* Am. Jour. Sci. and Arts, 3d ser., vol. xiv. 



t U. S. Geo. Expl., 40th Parallel. 



i Bull. U. S. Sur., vol. iii.. No. 3. 



§ Wheeler's Sur. W. 100th Mer.. vol. iv. 



II 10th Ann. Rep. Hayden's U. S. Geo. Sur. Terr.' 



