264 STANTON 



of the Fort Union. A few fragmentary mammals remains, among 

 which Mr. Gidley has identified ClcBnodon sp. nov., and MioclcEnus? 

 sp., were obtained from about the same horizon which, it should be 

 remembered, is above the highest recorded occurrence of dinosaurs 

 in the region, and fully 2000 feet above the highest horizon where 

 dinosaurs are abundant and positively known to occur. 



The most important collections of mammals were found in the 

 middle member ("Fort Union No. 2"), and especially in the quarry 

 opened in a thin sandstone 65 feet below the top of the member on 

 the east side of Bear Butte in sec. 4, T. 5 N., R. 16 E. On preliminary 

 examination Mr. Gidley has recognized Ptilodus montanus Douglass, 

 P. gracilis Gidley, P. serratus? (Marsh), P. formosus? (Marsh), 

 Mioclanus sp. nov., Euprotogonia sp. nov., Didymictis sp.nov., 

 Ectoconus? sp. nov., Deltatherium? sp., Psittacotherium sp., Chriacus 

 sp., Pantolamhda sp., Oxyclanus sp., Tricentes? sp., Pentacodon? sp., 

 Mixodedes? sp. The two doubtfully determined species of Ptilodus 

 described by Marsh occur in the " Ceratopsbeds" of Converse County, 

 Wyoming. All the others are related to species in the Torrejon fauna 

 of New Mexico, which was originally included in the Puerco. Clceno- 

 donferox (Cope) and Pantolamhda cavirictiis? Cope, belonging to the 

 same general fauna, were obtained in Silberling's upper and thicker 

 member of the Fort Union, the sandstones of which yield abundant 

 remains of a typical Fort Union flora. The upper and middle mem- 

 bers also yielded the reptiles Champsosaurus puercensis? Cope and 

 Crocodilus sp. 



In both the middle and the upper members fresh-water shells are 

 common at several horizons. They include Campeloma multilineata, 

 which in some of its varieties ranges from the Laramie of the Denver 

 basin and the "Ceratops beds" into the Fort Union, Viviparus, and 

 several species of Unio, most of which appear to be undescribed. 

 The Unios are all of simple types and do not include any of the pecul- 

 iarly sculptured forms like those of Hell Creek, Converse County, 

 and Black Buttes. 



As compared with the Bull Mountains section the "Laramie" of 

 Fish Creek is much thicker, the lower and middle members of the 

 Fort Union (1300 feet thick) correspond lithologically and strati- 

 graphically with the 200 feet of shale on Dean Creek, and the upper 

 member, though much thicker, resembles the coal-bearing Fort Union 



