I 



1863.] MR. J. K. LORD ON TWO -NEW MAMMALS. 95 



any appreciable crest. The occiput is rather differently shaped, the 

 hinder central keel being a little more prominent. The scales of the 

 head, body, limbs, and tail are smaller and less raised. The limbs 

 are longer and more slender. 



This species is very different from the Chamceleo affinis of Riippell, 

 (which is the C. abijssinicus of the Berlin Museum), from Abyssinia, 

 which differs from both C. senegalensis and C. Icevigatus in the scales 

 being much larger and more convex, and in the scales of the ridges 

 of the head and back being larger than those on the neighbouring 

 parts, so as to form distinct crests ; and in C. affinis the body is 

 grey or blackish, with two or three broad, irregular-shaped, opake- 

 white spots, forming an interrupted streak on each side of the back 

 of the animal. 



This species may be thus described : — 



Chameleo l^vigatus. 



Grey or bluish in spirits. Scales small, flat, subequal, uniform ; 

 dorsal line, nearly smooth, scarcely crested. Belly with a crest of 

 larger acute white scales. Occiput slightly raised in the centre by 

 a slight keel ; the superciliary ridges and the central keel scarcely 

 dentated. The legs elongate, very slender. 



Hab. Khartoom. 



5. Notes on Two New Species of Mammals. By J. K. Lord, 

 F.Z.S., Naturalist to the British North-American 

 Boundary 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 formulae, as well as in habit, colour, size, and 

 habitat, to constitute a species 1 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, strongly defined differences of size and co- 

 lour, 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- 

 kno'vn 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 



