Berry and Gregory — Prorosmarus alleni. 



445 



come anchylosed as is the case in even the young walrus, but 

 remained separate, although the deeply corrugated surfaces 

 were closely appressed and doubtless firmly bound together by 

 ligament. (6) The coronoid process is relatively higher, more 



r'r^ ' 



Fig. 1. The type of Prorosmarus alleni, lower jaw (left ramus), external 

 view. One-third natural size. 



slender and more inclined backward than in Odobwnus. 

 (7) Viewed dorsally, the opposite mandibular rami rapidly con- 

 verge to a point opposite the first " molar " when they sud- 



Fig. 2. Lower jaw (left ramus), external view, of an old male Atlantic 

 Walrus (Odobamus rosmarus). One-third natural size. 



denly expand into a broad spatulate everted lower lip. In 

 cross section this region is broad at the top, narrowing rapidly 

 below (figs. 1, 4A). In Odohamus, on the contrary, the rostrum 

 is much compressed above and broadly convex below (figs. 2, 

 4C). (8) In Prorosmarus on the lower border of the jaw below 



