[899-] IVortman and Matthew, Ancestry of the Canidce, etc. II J 



so in Cyon. Premolars unusually large ; ni^ unusually small, 

 with internal cusp of the trigon reduced in Tem?wcyon, absent in 

 Cyon. Jaw unusually deep under premolars. 



The two are separated by the usual progressive characters seen 

 in all modern Canidae ; the hallux is much reduced, mt. ii fall- 

 ing from ^ to "I- the length of mt. in. The pollex suffers a 

 similar reduction from ^ to -^ of mc. in. The foot is elongated 

 and narrowed, the brain cavity increased, the skull shortened. 

 Premolar 2 has acquired a posterior cusp in Cyo?i, lacking in 

 Temnocyoji ; the internal cusp of the superior sectorial is more re- 

 duced in the modern species. In our skull of Cyon alpimis the 

 incisors show a small basal lateral cusp. All these are acquired 

 characters, most of them being developed in almost all species of 



Fig. 3. Temnocyon ferox Eyerman. Upper and lower teeth, three fourths natural size. 

 After Eyerman. 



dogs. We find no acquired characters in Temnocyon that Cyon 

 has not, nor any primitive characters in the latter that the former 

 has not. 



Cyon, with its congener Icticyon, retains more than any of the 

 other dogs the primitive short legs and long body. The tail is 

 much reduced in both genera. 



2. Related Genera. 



Related to the Dhole and Temnocyon, and distinguislied like it 

 by the trenchant heels to the molar cusps, are the modern Icticyon, 



