56 
each side of the lower jaw. The canine tusks, of which the specimen on the 
table is one, are from fourteen to twenty inches and more in length, and are 
frequently seven in width across the base. They assist the animal in clam- 
bering over the rocks, and perhaps also in dragging up algae, which, together 
with small shell fish and Crustacea, form its chief diet. 
The ivory of the tusks is of fine quality, and is much used by dentists. 
Fiber zibethicus. (The Musquash, or Musk-rat.) Mr. Leipner remarked : — 
This animal is only found in North America, frequently in places above 
20° of north latitude. It is dark brown on the upper portions of its body ; 
the neck, sides, and legs, are of a reddish hue, and below it is of an ashy 
grey. Its length is about two feet, the tail being nearly half. The incisors 
are peculiar from their bright yellow hue. The dentition of the Musquash is 
very typical of the order Rodentia, to which it belongs. The incisors are 
four in number, two in each jaw ; the canines are wanting ; and the molars 
are peculiarly plaited, and have no fangs. The incisors never fall out, but 
when the edge is rubbed off it is renewed by a constant upward growth of 
the tooth. 
Lepus variabilis. (The Arctic Hare.) 
The genus Lepus, the author said, might always easily be distinguished in 
other rodents by the presence of two accessory incisors in the upper jaw. 
This species of Hare differs from our common Hare Lepus timidus, from 
the shortness of its ears, and generally larger size of the body. It is very 
similar to the Irish Hare Lepus hibernicus, which species many authors 
regard as a mere variety of the Arctic form. 
Amongst the most remarkable of the birds exhibited by the author, were 
a fine specimen of the Haven, now becoming so scarce in England, a series 
of the Ptarmigan, showing the gradation from the summer to the winter 
plumage, an American Robin, a Golden- winged Woodpecker in magnificent 
plumage, and a fine pair of Pine Grosbeaks, or Hawfinches. 
The President, in inviting discussion, remarked that the author had 
raised some curious points in the course of his very interesting paper, more 
especially those in reference to the change of colour in hair and feathers on 
the approach of winter. 
A considerable discussion on this point ensued, in which Mr. S. H. Swayne, 
M.R.C.S., Mr. W. L. Carpenter, B.A., B.Sc, Mr. Leipner, and other Mem- 
