EXTINCT MAMMALIA OF NORTH AMERICA. 437 



together with small fragments of a jaw from the raiocene formation of Virginia, pre- 

 sented to the Academy by Prof. Holmes, of Charleston. 



The teeth, represented in figures 16, 17, plate XXX, two-thirds the natural size, in 

 their general appearance remind one more of the tusks of a Boar than they do those 

 of the Sperm Whale, with which Oryderocetus may have been related. They 

 are long and conical, one being nearly straight, the other strongly curved. Near the 

 apex they are rather ovoidal in transverse section, but towards the base assume a 

 more quadrate character. They are finely ridged longitudinally, and strongly 

 marked with annular lines of growth. The apex is worn on opposite sides in the 

 straight tooth ; all around in the curved one. The base presents a funnel-like pulp 

 cavity defined by the thin edge at the outer periphery of the base of the teeth, as in 

 the incomplete teeth of the Sperm Whales, and as in the teeth of the Crocodiles. 

 The teeth exhibit no distinction of crown and fang, no signs of enamel investment, 

 but are composed wholly of dentine, except that the straight specimen on one side at 

 the base presents a thin patch of cementum, apparently the remains of a more ex- 

 tended covering. 



The curved tooth in its perfect condition along the convexity has been about five 

 inches in length ; the diameter at base about eleven lines laterally and ten lines from 

 before backward. The straight tooth has been about the third of an inch shorter, 

 and slightly less in diameter at base. 



A fragment of the upper jaw accompanying the teeth, about eight inches long, 

 accommodated as many teeth. The alveoli were separated by thin partitions, and 

 their bottom was separated from the dental canal by a thick layer of porous bone. 

 Two alveoli, perfect at their outer parapet, are an inch and three-fourths deep by an 

 inch in diameter. The outer part of the jaw at the side of these alveoli is three and 

 a quarter inches deep. 



Prof Emmons has described and figured a tooth which he refers to Oryderocetus 

 quadratidens. The specimen was obtained from Pitt Co., North Carolina, and is 

 probably of miocene age. The tooth is of more robust proportions, more curved, and 

 more obtuse at the summit than in those above described. " It is somewhat quad- 

 rate or angular ; its transverse section is rather ovate, with the anterior part flat- 

 tened. Its base has a short conical pulp cavity less than an inch in depth." The 

 length of the tooth as represented in Prof. Emmons' figure is about six inches; its 

 diameter at middle over fourteen lines. 



Orycterocetus cornutidens. 



Leidy : Proc. Acad. Nat. Sc. 1856, 255. Emmons: Rep. N. Car. Geol. Surv. 1858, 211, Fig. 33. 



Cope : Proc. Ac. Nat. Sc. 1867, 144. 

 Onjctcrucctus crocodiUnus, Cope : Proc. Ac. Nat. Sc. 1867, 144. 



This species was first characterized from an isolated tooth found in the miocene 



