88 Cretaceoiis. 



name Pachydon, and afterward renamed Anisothijris by Mr. Conrad, 

 becanse the name jPachyodon had been previonsly used for another 

 genus. 



Of course, comparisons of the shells, from this formation v,dth those 

 of the Tertiary beds of the Atlantic and Pacific slopes, afford no aid 

 whatever in fixing its precise position in the series, because the species 

 from the latter are, almost without exception, marine types. There is 

 less diflficulty, however, in drawing parallels between it and the Terti- 

 ary deposits of the Upper Missouri country, by a comparison of fossils, 

 although the species are mainly diff'erent, so far as jet known, in these 

 two districts. At least two of the known forms, however, from the 

 Utah and Wyoming beds under consideration, are believed to be spe- 

 cifically identical, with species found in the oldest beds, referred to the 

 Tertiary at the mouth of the Judith river, on the upper Missouri, 

 under the name of the Fort Union Group. These are Unio priscus, 

 and Viviparus conradi. In addition to this, the fossils at these two 

 localities are in precisely the same state ot preservation, and have a 

 more ancient appearance than those of the later deposits of both dis- 

 tricts, while they also agree exactly iu their mixture of brackish 

 and fresh water characters. Again, at both localities, these deposits 

 are intimately associated, as already stated, with what appears to be 

 the latest of the Cretaceous series; while in both districts they contain 

 lignite, and are succeeded by later Tertiary beds of strictly fresh water 

 origin. 



He described,* from the Fort Pierre Group, near the great bend in the 

 Upper Missouri,* Isocardia hodgei, now Procardia hodgei. 



Prof. 0. C. Marshf named, from the Niobrara Group, on the North 

 Fork of the Smoky river in Kansas, Edestosaurus dispar, now Cli- 

 dastes dispar, E. velox, now C. velox, CUdastes pumilis, C. wymani, 

 and Pterodactylus ov'eni.\ 



Prof. E. D. Cope described,^ from the Niobrara Group, near Fossil 

 Spring canon, Edestosaurus stenops, now CUdastes stenops-. E. tortor^ 

 now C. tortor, Holcodus coryphams, now Platecarpus coryplunus^ 

 Liodon cxrtirostris, now P. curtirostris, L. glandiferus^ now P. glan- 

 diferus, Portheus molossus, P. apgulatus, now Erislchthe angulatus ; 

 from Butte creek, Holcodus tectulus, now Platecarpus tectulus, Pro- 

 tostega gigas ; and from one mile southwest of Sheridan, near the 

 Gj^psum Buttes, Liodon latispinus, now Platecarpus latispinus. 



-■' Proc. Acad- Nat. Sci. 



t Am. Jour. Sci. and Arts, 3d series, vol 1. 



X Proc. Acad. Nat. Sci. § Proe. Am Phil. Soc 



