NOTES ON THE OSTEOLOGY AND DENTITION OF THE 

 GENERA DESMOSTYLUS AND CORNWALLIUS. 



By Oliver P. Hay, 



Associate of the Carnegie Institution, of Washington. 



From Dr. Edward M. Kindle, of the Canada Geological Survey, 

 tlie writer has received for examination a large tooth of Desmostylus, 

 which was presented to the Victoria Memorial Museum, at Ottawa, 

 by Dr. C. W. Newcombe, of Victoria, British Columbia. It had been 

 purchased from a dealer in curiosities and was reported to have been 

 brought from Alaska. This report may be true, but it is hardly to be 

 depended upon. The tooth no doubt belongs to Desmostylus^ but in- 

 asmuch as neither the locality nor the formation is known it would 

 be unsafe to identify it specifically. It appears to be a left upper 

 molar. 



Tlie tooth sent from Victoria (pi. 1, figs. 1, 2) had not yet come into 

 Ube, the unabraded sunmiits of its columns showing each the peculiar 

 depression and central nipple-like elevation. Only the base of the 

 root is present, and there are indications that it consisted of two 

 fangs. The greatest length of the tooth is 61 mm. ; the height 57 

 mm., including the base of the root. From the edge of the enamel 

 to the summit of the columns is 51 mm. The thickness, where great- 

 est, is 38 mm. The tooth consists of eight columns. Of these, three 

 form a front transverse row; then come two rows, each of two 

 columns; and at the rear is a single column. The transverse rows 

 are oblique to the axis of the tooth, being directed from the outside 

 inward and backward, as may be seen by figure 1 cited. 



As will be observed, the intervals between the columns are occu- 

 pied by cement, and this is of a lighter color than the surface 

 of the enamel. This cement rises from the root to the summit of 

 the columns. Below the bases of the second and the third columns 

 the cement continues to the center of the base of the root, lying 

 evidently in a valley which seems to mark the division of the root 

 into two fangs. The front of the tooth presents two tracts of 

 cement, one on each side of the median column, and it spreads over 

 the front of these anterior columns nearly half way to their sum- 

 mits. It is pro1)able that originally a large part of the crown was 



No. 2521 — Proceedings U. S. National Museum, Vol. 65, Art. 8. 



1 



