Mesozoic and Cenozoic Geology and Paleontology. 121 
Prof, O. C. Marsh* described, from the Miocene of the Rocky moun- 
tain region, Moropus distans, M. senex, and Allomys nitens; from the 
Green River Group of Wyoming, Heliobatus radians; and from the 
Pliocene of the Rocky mountains, Moropus elatus, Tapiravus rarus, 
Bison ferox, B. allent, and Crocodilus solaris. 
Prof. F. B. Meek} described, from the Miocene at Cache valley, Utah, 
Limnea kingt. 
Dr, C. A. White} described, from the Wasatch Group at Black Buttes 
Station, Wyoming, Unio provitus, U. holmesanus, U. endlichi, U. 
couest ; and from Wales, in Utah, and the Canon of Desolation, of 
Green river, Unio mendaz ; from the Tertiary,§ at Last Bluff, Utah, 
Physa pleuromatis ; and from Joe’s Valley, Viviparus tonicus. 
In 1878, Prof. C. A. Whitel| 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 passage 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, evidently 
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 ageregate 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. 
+ U.S. Geo. Expl., 40th Parallel. 
teBull Was. Sur., vol. iii. ,'No- 3: 
2 Wheeler’s Sur. W. 100th Mer., vol. iv. 
|| 10th Ann. Rep. Hayden’s U.S. Geo. Sur. Terr. 
