30 
the upper drab clay. Collections have also been made from the 
north slope of Como Ridge, from the outcrops 2 miles west of 
Steamboat Lake, and from the lower portion of the valley of Bone 
Creek. Bones have been found also at a point 2 miles east of Red 
Mountain, at several localities in Colorado a short distance south of 
the state line, in the slopes just west of Downey Lakes, and across 
Laramie River east of Jelm post-office. The drab, brittle, impure 
limestones occurring in the Morrison contain numerous remains of 
fresh-water mollusks which are usually of very small size. Fossil 
algae are not observed in the limestones in the Laramie Basin. Col- 
lections of mollusks made from various points have been identified by 
T. W. Stanton, as follows: West of Downey Lakes, in the NW. J 
sec. 15, T. 13 N., R. 75 W., TJnio baileyi, Valvata?, and Limnsea; at 
Riverside ranch, in the NE. J sec. 10, T. 13 N., R. 76 W., Planorbis 
vetemus, Valvata scabrida, Vorticifex steamsi, Viviparusf; on the 
ridge 3 miles south of Hutton Lakes, in the SW. \ sec. 32, T. 14 N., 
R. 74 W., Planorbis vetemus, Valvata scabrida, Vorticifex steamsi, 
Limnsea; on the road west of Homer's ranch, in the NW. \ sec. 11, 
T. 14 N., R. 74 W., Viviparus n. sp., "a large form wholly unlike 
anything previously reported from the Morrison;" on Como Ridge, 
in the SW. J sec. 9, T. 22 N., R. 77 W., Unio sp., Valvata scabrida, and 
Limnsea accelerata. 
In the thin layer of sandy limestone in the Morrison formation 
in the Freezeout Hills (bed 2.2, p. 29) Logan reports molluscan fauna 
as follows: Unio JcnigJiti, Z7. willistoni, TJ. baileyi, Valvata leei, and 
Planorbis vetemus. The two last named occur also in bed 21. 
Numerous cycads and pieces of fossil wood and a fragment of a 
hollow-boned dinosaur are reported from bed 18 in the same section. 
The dinosaurian remains in the Morrison formation have been 
regarded as Jurassic in age, but some eminent paleontologists now 
believe that they are early Cretaceous. As the stratigraphic rela- 
tions in some regions sustain this view, the formation is provision- 
ally assigned to the Cretaceous. 
CLOVERLY FORMATION. 
The Cloverly formation underlies a wide area in the Laramie Basin. 
Its outcrop zone extends all along the east side, crosses the south 
end of the basin, and follows an irregular course in the area of cross 
flexures west of McGill and north of Medicine Bow. It passes 
under the Tertiary deposits west of Marshall, but reappears in a small 
knoll 2 miles west of Little Medicine. For many miles along the 
west side of the basin from Laramie River northward it is dropped 
far below the surface by a great fault. There are prominent exposures 
west of Red Butte and in the ridges lying between Downey Lakes 
and Jelm Mountain. Small areas cap Red Mountain and the ridge 
next east, and the formation is exposed at points 2 miles west and 
