C. Marsh — Description of new fossil Serpents 



Art. ^J^Ylll.— Description of some new Fossil Serpmts, from 

 the Tertiary Deposits of Wyoming; by Professor 0. C. Marsh, 

 of Yale College. 



Among the Eeptilian fossils discovered by the Yale College 

 party, during their explorations last summer in the Grreen Eiver 

 Tertiary basin, west of the Eocky Mountains, were the remains 

 of several species of Serpents, which are of peculiar interest, as 

 they are the first extinct Ophidians found in the interior of the 

 continent, and, with the exception of three species from the 

 Eocene marl of New Jereey,* the only fossil representatives of 

 this order yet detected in this country. 



These remains, which are now in the Peabody Museum of 

 Yale College, 

 of them more ■ 



acteristic parts well preserved. Nearly all the specimens ( 

 tained evidently belonged to constricting serpents, closely re- 

 lated to the modem Boas of South America, although consid- 

 erably smaller, and generically tlistinct. A few of the specimens 

 indicate snakes of moderate size, with apparently quite different 



In comparing the larger series of these fossil vertebrae, espe- 

 cially those from near the middle of the trunk, with the coites- 

 ponding vertebras of the living species of Boa, a strong resem- 

 blance will be noticed in the more important characters, especially 

 in the transversely elliptical outline of the articular cup and ball; 

 in the obtuse lateral elevation extending from the diapophyses 

 to the articular ball ; and in the elongated median ridge on the 

 inferior surface of the centrum. The differences between them, 

 however, are important, and indicate clearly that the fossil 

 specimens represent a separate genus, for which the name 

 Boavus\ is proposed, in allusion to the not improbable relation- 

 ship of the two types. In the extinct genus, the articular ball 

 and cup are more neariy vertical, and their outline forms a more 

 full transverse ellipse. The neural arch is proportionally more 

 elevated, and has on either side a low ridge, extending backwara 

 from the articular face of the zygosphene, and expanding over 

 the zygantral cavities. The latter are more deeply excavatea 

 than in Boa. The neural spine is shorter, its antero-posterior 

 extent, in the specimens in which it is preserved, being greater 

 than its height. The diapophyses are convex throughout, w^r^ 

 those of ^a are more or less concave on the lower part of the r 

 articular .face. The lateral elevation, extending from the dia- 

 pophyses to the articular ball, is, in Boavus, situated lower on 



