Eocene, shows a remarkably close correspondence. This epoch, 

 the Suessonien of D'Orbigny (Orthrocene Gervais), includes the 

 marls of Rilly and lignites of Soissons, the Thanet sands, London 

 clays, etc. Fossils from these beds appear to have been no better 

 preserved than those of the Wahsatch beds of the Rocky Moun- 

 tains, yet some of the genera are identical, and others closely cor- 

 respondent, as follows : — 



Wahsatch. Suessonien. 



Ambloctonus. Palaonyctis. 



Hyracotherium. Hyracotherium. 



OorypJiodon. Ooryplwdon. 



Diatryma. Gastomis. 



Lepidosteus. Lejridosteus. 



As a point of difference between the beds, may be mentioned 

 the absence of the Tseniodonta from the Suessonien, a suborder 

 not yet known out of North America. 



The Wahsatch formation includes the Geeen River beds of Hay- 

 den, a name which I formerly applied to the entire series. It, 

 however, applies properly to the fish shales of Green River, con- 

 taining Asineops, Clupea, Osteoglossum, etc., which are probably 

 local in their character. 



The Bridger formation will then represent on the American 

 continent more nearly than any other, the middle Eocene or Pa- 

 risien of Cuvier, Brogniart, and Renevier. 



The teeth of sharks described in the reports quoted are of un- 

 certain origin. They are associated with oyster shells, and both 

 have the appearance of having been transported; nevertheless 

 some of the mammalian teeth found associated with them have 

 a similarly rolled appearance. It therefore remains uncertain 

 whether the ocean had for a limited time access to the Eocene 

 lake, or whether the shark's teeth and Ostrese were derived from 

 the cretaceous beds which formed its shores. Similar, and in one 

 instance the same species of sharks were found in both formations, 

 the division of the cretaceous being No. 3 and 4 of Hayden. 1 



In conclusion, the classification of the North American Eocene 

 may be represented as follows : — 



Formation. Equivalent. Locality. Characteristic Fossils. 



(Palcsosyops, 

 Tillodonta. 

 Dinocerata. 



Wahsatch. Form. Lower Eocene. \ 



f N. B , % wMe*i-f?3 S //X 



{ oo, 8.W. Wyo- j Phenac „ dm [ 

 (_ mmg. ^ Diatryma. 



1 The same state of things exists in the siderolitic deposits of the canton 

 of Vand, Switzerland. Mingled with the mammalian remains are teeth of 

 sharks, of which M. La Harpe remarks that their appearance does not war- 

 rant the belief that they have been transported, or are not indigenous to the 

 Eocene fauna. 



Published April 26, 1876. 



