CIIAPTER II 



THE LOWER JAW. 



(Plates VIII, . XII, XIII, XIX, LV, and LVI.) 



The lower jaw in Binoceras is as remarkable as the skull. Its most 

 peculiar feature in the male is a massive decurved process on each ramus, 

 extending downward and outward. These long- pendent processes were 

 apparently to protect the iii)})er canine tu.sks, which would otherwise he 

 \'ery liable to be broken (Plate XIII, figures 1 and 2, j/). Indications of 

 similar ])rocesses are seen in Smilodon, and in some other extinct carnivors 

 with long canines. 



In JDiiwceras mirahile (number 1212), the process is concave from above 

 downward on its external surface, and its lower extremity is somewhat 

 thin, and narrowed longitudnially. In D'moceras hiticcps (Plate XIII, 

 figures 1 and 2, p), this process is more massive, and more rounded below. 



In the female, this process is much reduced in size, but is quite 

 sufficient to protect the diminutive tusk, which overlaps it. 



With the exception of these processes, the lower jaw is comparatively 

 small and slender. The symphysis is completely ossified, and deeply 

 excavated above. 



Another remarkable feature in the lower jaw of the Dinoceruta is the 

 posterior direction of the coitdyles, hitlierto miknown in Ungulates (Plate 



