548 
OBSERVATIONS ON TllE 
XLV.- — Observations on the Anatomy of the 
Beaver, (Castor Fiber, Linn.), considered as 
an Aquatic AnimaL 
By R. Knox, Esq. M. D. M. W. S. 
and Member of tlie Medico-Chirurgical Society. 
{Read imh April 1S23.) 
opportunity having occurred to me lately of dissecting 
the Canadian Beaver, a few anatomical facts presented them- 
selves^ which apparently have hitherto escaped notice. Of 
these, one is in a remarkable manner connected with the 
habits of aquatic animals, and more especially with the 
power they possess of remaining for a considerable time 
under water. I shall now submit an account of these to 
the Society. 
The specimens, two in number, were both females : their 
exact weight is unknown, but the cartilaginous condition of 
the bones demonstrate them to have been young animals. 
During a hasty examination of the integuments, I observed 
the supernumerary nail on one of the toes of the hind leg, a 
pecuharity known to exist in the Beaver of the Rhine and 
