o*e © 
64 “Dr. J. Woman on Fossil Bones jrom Memphis, 7 Tenn, 
tooth. The outer groove is situated between: ats saleul and. 
third plates and the inner between the second a rst, but in» 
consequence of. the obliquity of the third plate, are ee Oppo- . . 
site. The fourth tooth is the smallest, the lamine are all nearly 
parallel to each other and the Tateral grooves are much less deep 
than in sa preceding teeth. 
It not appear from any examination which I have made . 
pe 
of the laexal teeth, that the different lamine are united togeth- _ 
er at their bases by a continuous layer of enamel passing from — 
one plate to the other, as is the case in the teeth of the elephant. — 
Each tooth appears to be made up of a series of flattened denti- 
nal sohucties invested with enamel and simply cemented together 
by crusta petrosa 
The incisor tooth in a transverse section is of a triangular form, 
with rounded angles; its inner face smooth and concave, its an- 
terior convex and fluted with well a ea parallel grooves, and its 
posterior convex and smooth. ouble curvature of this tooth 
is quite remarkable ; when od laterally its curve is that of 
the segment of a cirele : when viewed from below it has a curv- 
ature in a plane at right angles to the preceding, which curve as 
is shown very distinctly in the cast of Mr. Foster’s specimen is 
in the form of an./, as is,the case in the beaver and many other 
Rodents. If both of these: curves were continued they would 
produce a spiral. It is well known that the incisor teeth of 
Rodents are constantly wearing away at the apex, and are as 
constantly replaced at the base, so that if we would suppose the 
growth continued through life, and that no abrasion took place, 
there would be lies produced a spiral of several revolutions 
in the form of a cork-screw. We have an approximation to this 
in Rodents which have lost one of their incisors, and in whom 
the opposite one no longer worn off, has continued - increase in 
length sometimes forming more than one revolution. 
The remains of the Castoroides though they have edo been 
found, have nevertheless as already stated, a wide geographical 
distribution, having been discovered in New York k, Ohio, Tennes- 
see and Louisiana, and in all these localities except New York, 
have been associated with the remains of the Mastodon; and Mr. — ; 
Hall refers the deposit in which the New York specimen waS 
found to the same period as the deposits in which the Mastodon 
has been discovered in the neighboring portions of that state.t 
It is also interesting to notice the existence of the remains of 
Castor and Castoroides in the same localities, one of which con- 
tinues to the present period, and the other, the gigantic representa- 
tive of the Rodents, has disappeared with the corresponding oné 
of the Pachyderms. 
ens 637 and 838. 
| act i soa i etme 
Castoroides Ohioensis—By James Hall, Esq., and Dr. J. Wyman. Boston Jour 
nal of Nat. Hist, vol. v, p. 884. , 
Lee 
. 
