Cope.] ^O [Jan. 5, 



to the edge of the ball of the centrum. Below this the surface is slightly 

 concave, and the middle line is gently convex. The latter terminates in 

 an obtuse angled mark just in front of the edge of the ball. This edge is 

 also slightly free from the ball. The capitular costal surfaces do not pro- 

 ject inferiorly quite to the line of the inferior surface of the centrum. 



Measurements of a Vertebra. M. 



Length of centrum (with ball) 0070 



c vertical 0035 



Diameters of ball j trangverse 0(M0 



• Elevation of vertebra at episphen .0085 



middle 0062 



Width at prezygapophyses ' 0120 



" tubercular costal faces 0105 



" of zygantrum. 0058 



Vertical diameter costal faces 0040 



Transverse diameter tubercular costal face 0028 



This snake was about the size of the black snake, Bascanium constrictor. 

 It is an interesting species for two reasons. First, it is the oldest serpent 

 known from North America. Second, in the imperfection of the zyiian- 

 trum we observe an approximation to the ordinary reptilian type of verte- 

 bra, from which the ophidian type was no doubt derived. In the former 

 there is no zygosphen or zygantrum. 



Mammalia. 



Triisodon levisianus, sp nov. 



This creodont is represented by part of a right mandibular raums which 

 contains the fourth premolar minus its principal cusp, and the first and 

 second true molars, with the alveoli of the third. The ramus is deep, and 

 probably belonged to an animal of about the size of the red fox. The molars 

 have the structure most like that of the T. heilprinianus, especially an- 

 teriorly. The principal anterior cusps are united together for most of their 

 elevation, while the anterior inner is much smaller and lower, and is situ- 

 ated between the middle and inner side of the anterior cusp. The heel is 

 rather wide, and has a raised border. The external part of it is angular, 

 and is somewhat within the vertical line of the base of the crown. The 

 fourth premolar differs from that of the type the genus, T. quivirensis, 

 in having two acute longitudinal tubercles situated close together on the 

 heel. 



The anterior masseteric ridge is very prominent. The masseteric fossa is 

 strongly concave, but shallows gradually inferiorly. Its inferior border 

 presents a low thickened ridge, which is recurved in front. This may be 

 an individual character only. The inferior outline of the ramus is gener- 

 ally convex, and does not rise much below the masseteric fossa. 



