292 Worlman — Studies of Eocene Mammalia in the 



figures of M. lanius, as given by Cope, there is no such 

 arrangement of inferior canine and incisors as above described. 

 It may possibly be that the condition of Cope's type of M. lanius 

 is abnormal in this respect, and that Dromocyon vorax is the 

 same as M. lanius y but until this is confirmed or disproved 

 by additional specimens, I feel bound to regard the two forms 

 as distinct. A further reason for such a course lies in the fact 

 that the two specimens are from widely separated localities in 

 different basins, M. lanius coming from the Washakie, and 

 Dromocyon from the Bridger. 



The Skull. (Plates II-IV.) — Like all members of the Meso- 

 nychidae thus far known, the skull is large in proportion to 

 the size of the body ; its length is equivalent to that of 15|- 

 vertebrae counting from the first dorsal backward, or it is about 

 one and one-half times the length of the femur. When com- 

 pared with a large specimen of Canis familiaris (Bloodhound), 

 the size of the two skeletons being about equal, the length of 

 the skull is seen to be quite one-half greater. In this specimen 

 of the clog, the length of the skull is equal to that of only 10 

 vertebrae counting from the first dorsal backward, or is just 

 about equal to that of the femur. 



The muzzle is of moderate length and height, slightly con- 

 stricted behind the canines, and obliquely truncated in front. 

 The anterior narial opening looks forward and a little upward. 

 The premaxillae exhibit the form and relations usual among 

 the Carnivora ; they articulate freely with the nasals above, 

 but do not send up a process to join the frontals behind, as in 

 many Carnivores. The nasals are broad posteriorly, and in 

 connection with the lachrymals almost exclude contact between 

 frontals and maxillae, as in certain carnivorous Marsupials, 

 notably Sarcophilus and Didelphys. As in these latter forms, 

 owing to the large size of the lachrymals, the maxillae are 

 excluded from any share in the boundary of the orbit, whereas 

 in all the Carnassidents, with the exception of Eupleres, the 

 posterior edge of the maxillary reaches the anterior rim of the 

 orbit. The infraorbital foramen is large, and has its usual 

 position above the posterior border of the third premolar. The 

 orbit is relatively small, as in Sarcophilus and the opossum, in 

 marked contrast with its large size in the great majority of the 

 Carnassidents : its anterior border lies above, and coincides 

 with, the anterior edge of the second molar. As already men- 

 tioned, the lachrymal is large and spreads out upon the face to 

 a considerable extent; it carries a very prominent lachrymal 

 tubercle, as in many of the Marsupials, but the lachrymal canal 

 is simple and opens within the rim of the orbit, as in the Car- 

 nassidents. There are well-developed postorbital processes of 

 the frontals, and corresponding though less distinct processes 



