EXTINCT MAMMALIA OF NORTH AMERICA. 



439 



Length in present condition in a straight line, 



Estimated length of fang restored, 



Greater diameter of fang, 



Lesser diameter of fang, 



Estimated diameter of crown at base, . 



Lines. 

 44 

 52 

 19 

 16i 

 8 



of an axis of dentine about equal in 



The fang of this tooth appears to consist 

 diameter to the crown, and its great accession of bulk appears to be due to the ce- 

 mental layer. 



The second specimen consists of the fragment of a tooth devoid of crown. The 

 tooth has been of little greater bulk than the preceding, as the diameter of the re- 

 maining portion of the fang is twenty and one-half lines. 



The more perfect tooth bears a near resemblance to that of Hoplocetus crassidens, 

 represented in figure 10, plate XX, of Gervais' Pal^ontologie Francaise. 



Another tooth referable to the same genus, and perhaps to a ditferent species, is 

 represented in figures 14, 15, plate XXX, two-thirds the natural diameter. It was 

 sent to me for examination by Prof. Wyman, of Cambridge, and was derived from 

 the miocene formation in the vicinity of Richmond, Virginia. It is much larger and 

 straighter than the better preserved of the two specimens above described. 



The crown is worn off in a blunt manner or somewhat convex disk, about nine 

 lines in diameter, and is encircled by a more or less worn and broken band of longi- 

 tudinally rugose enamel, varying in depth from three to five lines, and one-third of a 

 line in thickness. The fang is broken at its end, and exhibits a long conical pulp 

 cavity, large enough to introduce the end of the middle finger for an inch or more. 

 The fang in shape is fusiform, exceedingly robust, straight, and somewhat quadrate. 

 As in the other specimens, it is composed of a dentinal axis near the diameter of the 

 crown, enveloped in a huge accumulation of cementum. The length of the specimen 

 in a straight line, in its present condition, is fifty-five lines. The fang in a restored 

 condition is estimated to have been five inches long. The diameter of the fang is 

 twenty and twenty-one and a half lines. 



In the large proportion of cementum to the dentinal axis of the teeth of Hoplocetus 

 they bear such a resemblance to the fragments found in the Red Crag of England, 

 and referred by Prof. Owen to a genus under the name of Balcenodon, as to render it 

 probable the former is the same as the latter. 



The relations of Hoplocetus oy BaJcenodon are conjectural; though associated with 

 the cetaceans, the teeth upon which the genus is founded remind one quite as much, 

 if not more, of the canines of certain Seals. 



