1898.] Osl)orn, Evolution of the Aniblypoda. Part I. 



21 I 



sharp external ridtje. Lower canines with short external ridge near apex. 

 Second incisors enlarged ; lateral incisors much reduced. Posterior inferior 

 molars with crests mort- transverse than in C. testis (angle = 74'^) a persistent 

 entoconid 2. ( ? Cuneiform articulating with Mtc. V.) 



'riiis species is clearly distinguished from C. testis by the 

 foiin of the canines, which in this animal are comparatively 

 straight and lance-shaped (Fig. 17), the long axis transverse 

 (unlike Uintat/ierii///i), with an antero- internal groove which is 



l^^ 



A 



Fig. ^6. Foot structure of Coryf>hodon. D, external view of manus of C. ventanus (No. 

 4351, Coll. Am. Mus.) ; .-I, superior view of astragalus and calcaneum found near C. stilus, 

 no tibial facet (Bathmodon type); B, lower surface of astragalus, showing calcaneal and 

 cuboidal facets ; C, external view of calcaneum and astragalus, showing reduction of tibio- 

 calcaneal facet. (Coll U. S. Nat. Mus.) 



worn away by the lower canine. They resemble those of C. lati- 

 dcns Cope (e.xcept in the groove), but are much less compressed 

 than those of C. aniiatiis Cope, besides having the long axis in a 

 different plane. The posterior crest of nig (Fig. 16) differs from 

 those of C. armatus and C. siinus in form and in the retention of 

 an entoconid 2, and from that of C. testis in being slightly less 

 oblique. y\nother character is the very ra])id increase in size of 

 the molar series as we pass backward : mi = 28, m3 = 42. 



To this species belong Nos. 2982, 4813, 4812, 277^5, and 2978 

 of our collection. The latter contains the complete lower teeth 

 which exhibit the marked disproportion between the second and 

 the first and third incisors embodied in the definition of this spe- 

 cies. The incisor proportions are indicated by the length of 

 roots, i 1 = 36, i 2 = 59, i 3 = 28. 



