Marsh Collection, Peabody Museum. 291 



Dromocyon vorax Marsh. 



Dromocyon vorax, Marsh. This Journal, vol. xii, July, 1876, p. 403. 



The second genus of this subfamily to be considered is 

 Dromocyon, and fortunately the remains upon which it was 

 founded consist of a nearly complete skeleton of a single indi- 

 vidual, in magnificent preservation. In his original description 

 of this genus and species, Professor Marsh states : u A new and 

 remarkable carnivorous mammal about the size of a large wolf 

 is represented in the Yale Museum by a nearly complete skel- 

 eton. In the form of the skull, and general character of the 

 jaws and teeth, the genus resembles Hycenodon. In the pres- 

 ent specimen there were apparently but two lower incisors in 

 each ramus. There are seven lower molar teeth, and the last 

 lower molar is small. The top of the skull supported an enor- 

 mous sagittal crest. The brain was small and convoluted. 

 The lower jaws are long and slender, and the condyles low. 

 The femur has a small third trochanter, and the astralagus a 

 facet for the cuboid. There were four toes in front, and four 

 behind." 



This description, as will be seen from the analytical table 

 given above, does not distinguish the genus sufficiently from 

 Mesonyx or other members of the subfamily. Cope recognized 

 two species of Mesonyx from the Bridger horizon, M. obtusi- 

 dens and M. lanius* The latter of these was originally 

 described as a separate and distinct genus, Synoplotherium, 

 which, however, was afterward abandoned as indistinguishable 

 from Mesonyx. The type specimen of M. lanius consists of a 

 portion of the skull, together with one fore foot more or less 

 complete, and numerous fragmentary parts of the skeleton of a 

 single individual, from the lower levels of the Washakie Basin. 



Of this specimen, which is the only one thus far known, 

 Cope,f in speaking of the incisor region of the lower jaw, says : 

 " The most remarkable feature of the genus is seen in the 

 inferior canines. These are very large teeth, and are directed 

 immediately forwards, as in the cutting teeth of rodents. They 

 work with their extremities against the retrorse crowns of the 

 two external incisors above, and laterally against the superior 

 canine. They are separated by a space about equal to the 

 diameter of one of them. In this space I find no alveoli nor 

 roots of teeth ; the outer alveolar wall extends far beyond the 

 inner. The latter terminates opposite the middle of the supe- 

 rior canine. It may be that there are no inferior incisors." 



While the structure of the fore foot as well as other com- 

 parable parts of the skeleton of Dromocyon vorax agree very 

 closely in size and other respects with the description and 



* Tertiary Yertebrata, J 884, pp. 348, 362. f Loc. cit.. p. 359 



