from the. Tertiary deposits of Wyoming. 325 



The specimens here described were found by H. B. Sargent, 

 in the same fresh-water Tertiary deposits, and near the same 

 locahtj, as the two preceding species. 



Lit! I aphis Sargenii^ gen. et sp. no v. 

 This species and genus are at present represented by three 

 trunk vertebrae, only one of which, however, is sufficiently 

 well preserved to show all its more important characters. The 

 specimens indicate a small serpent about four feet in lenath, 

 and probably, like the preceding species, allied to the constric- 

 tors. From the vertebras of Boavus, as well as from those of 

 the other fossil Ophidians discovered in this country, the pres- 

 ent specimens may be readily distinguished by the more com- 

 pressed centrum, and especially by the articular cup and ]>all, 

 which are circular in transverse outline, as in the Arican Myx, 

 and stand nearly at right angles to the axis of the centrum. 

 The anterior zygapophyses, also, are more extended outwnr i. 

 and their articular faces" have a greater aiitero-posterior exp,: 

 sion than in any of the described species. The diapoph\- 

 jiave their articular surfaces divided by a horizontal grou\. . 

 having a rounded tubercle above, and" a pointed projectiuk 

 below, as in the modern Ba^canion. There is no lateral ridge 

 extending from the diapophyses to the articular ball, as in Boa 

 and Boavus, the converging sides of the centrum being nearly 

 nat The hypapophysis is reduced to a wedge-shaped ridge, 

 extending the whole length of the centrum, and having its 

 sharp apex below the inferior margin of the cup. The floor 

 01 the neural canal has a prominent, obtuse median ridge 

 throughout its whole length, but no lateral ridges are apparent. 

 J- he principal measurements of the best preserved vertebra 

 are as follows : 

 I^ength of centrum from edge of cup to convexity of ball, 2-80 lines. 



Iranaverse diameter of cup, 1'35 " 



Vertical diameter of cup,.". 1-35 " 



X^.^Jical diameter of ball, 1-30 " 



H idth of neural canal in front, --- '90 " 



AJistance from end of anterior zygapophysis to hypa- 



Pophysis, 3-00 « 



distance between ends of the anterior zygapophyses, . 4-50 " 



For the extinct genus manifestly indicated by the. fossils here 

 Jlescnbed, the name Lithophis* is proposed, and the species 

 they represent may appropriately be called Lithophis Sargenii, 

 after the discoverer, Mr. H. B. Sargent, of the Yale Scientific 

 party, who found the specimens in the Eocene "Mauvaises 

 J-erres" beds at Grizzly Buttes, near Fort Bridger. 

 * Atflof, stone, and 'O^if, serpent. 



