MESODONTA. 
137 
Carnivora. Of the species from the New Mexican Eocene, now included 
in it, only the dentition is known, and that incompletely. The T. jarrovii 
differs in several respects from the T. rostratum. Thus, in the latter, the 
first true molar is the only one in which the anterior inner tubercle is 
represented by two separated cusps; in T. jarrovii, this peculiarity charac¬ 
terizes all the true molars. In T. rostratum, the second premolar is one- 
rooted; in T. jarrovii, two-rooted. In the T. frugivorum, the true molars are 
similar to those of T. jarrovii. It is possible that these species will be found 
to be worthy of separation from Tomitherium as a distinct genus, as I have 
already proposed, and require the use of the name of Pelycodus (Systematic 
Catalogue of the Vertebrata of the Eocene of New Mexico, 1 «75, p. 13). The 
teeth of the species described as P. angulatus resemble those of Microsyops, 
but the dental series is not sufficiently complete to warrant its final generic 
reference. 
Tomitherium jarrovii, Cope. 
Plate xxxix, tigs. 17-18 ; Plate xl, tigs. 1-15. 
Prototomus jarrovii. Cope, Eeport Vert. Foss. New Mexico, IT. S. Geog. Survs. W. of 
100th M,, 1874, p. 14; Id. Ann. Eeport U. S. Geog. Survs. W. of 100th M., 
1874, p. 126. 
Pelycodus jarrovii. Cope, System. Cat. Vert. Eocene New Mexico, U. S. Geog. Survs. 
W. of 100th M., 1875, 13. 
This species is rejiresented in the collections of the Survey by a 
fractured right mandibular ramus, each fragment supjiorting a molar tooth, 
accompanied by bones of a skeleton which probably belong to it; also by 
part of the right mandibular ramus of another individual, with the last 
two molars; probably also by a mandibular fragment of a third, with a 
premolar tooth in position. 
The second specimen displays the last molar. The base ^f its crown 
is an elongate oval, narrower behind. It supports two low cusps in front, 
a lobe on the middle of its outer border, and a lobe-like heel. The inner 
border is low, and continuous to the anterior cusp. The latter has a small 
tubercle on its anterior border, which is continued into the border of the 
crown without interruption to the anterior outer cusp. The center of the 
crown is concave and basin-shaped; an external cingulum at the front of the 
crown only. 
In the second specimen, the ramus is thick and moderately deep, with 
