Zoological Society. 93 
PROCEEDINGS OF LEARNED SOCIETIES. 
ZOOLOGICAL SOCIETY. 
March 24, 1863.—W. H. Flower, Esq., F.Z.S., in the Chair. 
Notes on Two New Species oF Mammats. By J. K. Lorp, 
F.Z.S., NarurRALIST TO THE British NortH-AMERICAN 
BounpaAry ComMISSION. 
My principal reason for bringing to your notice this evening two 
animals, a Musk Rat and a Lagomys, that I propose making new 
species, is to elicit from the zoologists who are before me opinions 
on that most debatable of all debatable questions, Where does well- 
marked variety end, and species begin? Is it enough if you have 
decided differences of habit, size, colour, and locality —variations 
that are always constant, but without well-defined structural differ- 
ences, or these, if any, but trivial in character; or must there of ne- 
cessity be decidedly marked variations in structure, particularly in 
the skull and dental formule, as well as in habit, colour, size, and 
habitat, to constitute a species? I now have on the table four ani- 
mals, two of which are described and figured, and two I believe 
specifically distinct from the former ; and although the latter, as I 
shall be able to point out to you, present differences of habit most 
singularly well marked, and strongly defined differences of size and 
colour, habitat, and range, yet an examination of their skulls shows 
only some slight differences, principally in size. 
First, then, of the Musk Rat. The one which I believe is the well- 
known Fiber zibethicus (Cuv.) makes its holes in the clayey banks 
of streams and pools where the water runs slowly. The entrance is 
always below the surface of the water; the hole is dug up in a 
slanting direction till above the water-level. A stage or flat place is 
then cleared, which constitutes his dining-, drawing-, and bed-rooms ; 
leading to the entrance of his mansion are a large number of open 
cuttings, running in all directions, cut or dug in the mud at the bot- 
tom of the water. When foraging about, as he usually does about 
twilight, if alarmed, he dives at once into one of these cuttings, and, 
rushing rapidly through it, stirs up the mud, and so fouling the 
water, completely and effectually conceals himself. 
The other Musk Rat, which I propose to make a new species, and 
to call Fiber osoyoosensis, having obtained it at a large lake (Lake 
Osoyoos) situated between the Cascades and Rocky Mountains, and 
through which the boundary-line (the 49th parallel of latitude) runs, 
differs in size, in colour, in locality, but particularly in habits, from 
the preceding. 
This fellow chooses as his haunt a clear pond or lake, and in water 
frém 3 to 4 feet deep constructs a house of bullrushes, in form 
conical, built up from the bottom—how, I am at a loss to imagine,— 
the roof cleverly arched over into a domed shape, and raised about 
a foot above the water. Up in this dome, skilfully constructed, is 
his suite of apartments, the entrance to which is far below the sur- 
