634 Troxell — Vertebrate Fossils of Rock Creek, Texas. 



Canis so3vus Leidy has recently (13.219) been classed 

 under ^Ehorodon swvus. 



Canis mississippiensis Allen is based on a tibia and humerus ; 

 only the latter is capable of comparison with the paratype 

 humerus (fig. 23) of C. texanus. Group II, which includes the 

 type of C. texanus, is very near C. missi ssippiensis in size, 

 but the character of the dentition cannot be compared. 



Canis texanus as a new species is distinguished from the 

 wolf in the greater curve and twist of the ramus and in its 

 greater depth ; in the prominent cusps of P 4 , which slope in- 

 ward and backward ; in the talonid of M„ which has a single 

 large cusp ; and in the weak metaconid of M 2 . 



C. priscolatrans, giving a ratio of 106, is 22 per cent larger 

 than the molar (tig. 19) of group III, but the written descrip- 

 tion conforms well with this tooth. C. priscolatrans may not 

 be distinct from C. mississippiensis nor C. texanus, n. sp. 



The group IY, which is composed of two bones (figs. 21, 22), 

 shows an average ratio of 65 per cent ; this is nearest C. teme- 

 rarhis Leidy, which gives a ratio of 69 per cent to the recent 



do 2- 



C. vafer Leidy, with a ratio of 49 per cent, seems too small 



to be referred even to the small bones of group IY. 



The phylogeny of the Canidse is not well known, even though 

 this group is native to North America. The ancestry is traced 

 back through Tephrocyon to Cynodesmus and then lost in pri- 

 mordial obscurity. The descendants of these early forms are 

 represented to-day by our dogs, wolves, and foxes, and the recent 

 animals are almost indistinguishable from the fossils. 



Carnivores are much more difficult of preservation than other 

 animals, and it is quite unusual for fossil remains of this order 

 to be found. They usually roam about singly or in small groups. 

 They are wary animals, with a keen sense of danger, and are 

 necessarily much fewer in number than the herbivores on 

 which they feed. 



The fossil dogs give us little knowledge of their environ- 

 ment. The large heavy beast referred to C. dims may be the 

 analogue of our timber wolf; the smallest, identified as C. tem- 

 erarius, may represent the fox. Either would be best adapted 

 to a timbered country. C. texanus, n. sp., and C. priscolatrans, 

 represented by the single molar, may be analogous to the 

 prairie wolf or coyote, a swifter type preying upon the curso- 

 rial plains dwellers. It is not strange that we should find the 

 species commingled, since even to-day, in the Panhandle of 

 Texas, we find the great Lobo or timber wolf and also the 

 coyote. 



