190 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
information respecting Richardson’s types, now in the British museum. 
The case appears to stand thus:— 
Richardson says (F. B.-A. i, p. _) that “five species are common in the 
Hudson’s Bay regions, exclusive of the lemmings”. These, according to his 
views, are (1) “ziparius Ord”; (2) “xanthognathus Leach”; (3) “ pennsylva- 
nicus Ord”; (4) ‘noveboracensis Raf.”; and (5) “borealis Rich.” Now there 
is no reasonable doubt that all five of these ‘‘common” species are repre- 
sented in our immense series; but the difficulty is twofold. In the first 
place, it is to the last degree improbable that there are five species at all. 
Richardson’s four lemmings have to be reduced to two, and there is no ques- 
tion that the grade of characters he sometimes employed to distinguish supposed 
species are utterly fallacious. Next, whatever the true number may be, we 
cannot make out, from Richardson’s descriptions. which is which. This may 
seem strange, seeing the apparent minute detail of Richardson’s descriptions ; 
but, when we come to sift out his accounts, we find that three-fourths of all 
he says is generic (even ordinal) in character, and consequently pointless. 
Audubon’s and Bachman’s accounts are still more faulty in this respect ; 
these gentlemen knew nothing about the animals they described except what 
they got from the Fauna Boreali-Americana. We will first expose the futility 
of what seem to be two strong points in these authors’ accounts :— 
Respecting his “riparius Ord” (afterward “richardson A. & B.”), 
Richardson says that the “incisors are twice the size of those of A. xanthog- 
nathus, although the latter is the larger animal of the two”. And regarding 
his “‘ borealis”, Richardson says:—“It is distinguished by the form of the 
thumb-nail” * * &c. Now,after examining hundreds of Arctic Arvicola, 
we have seen nothing of the sort in the matter of the incisors or of the nail, and 
must conclude that either we have not got hold of Richardson’s animals, or 
else that there is some mistake about the alleged characters. The former 
supposition is untenable, for we have plenty of skins that show exactly all 
the other ascribed characters of “riparius” and “borealis”. We therefore 
ignore these points altogether. 
The ‘‘noveboracensis? Raf.” of Richardson (afterward drummondiu A. & 
B.) seems to be different from the rest, and perhaps does not belong to the 
riparius section at all. Professor Baird surmised that it might be a Pedomys, 
and we once rather inclined to the same opinion. It is described as having 
the “ears slightly overtopping the fur”; the “ventral aspect yellowish-gray” 
