MAMMALIA. 
41 
Proceeding now to the question of nomenclature, it may be as well, before making 
any remarks upon it, to quote Mr. Blyth’s description l. c. in full. It runs as follows ~ 
PhAiomys, nobis, n. g. Similar to Arvicola, but more robust, with a well-developed thumb and nail to the 
forefoot; tail shortish and densely clad with short adpressed hairs. Upper rodent tusks inconspicuously grooved. 
Ph. leucurus, nobis, n. s. Length of a female containing si xfcstus inch, of which tail \ inch ; l of a 
smaller specimen sent inches, of which tail If inch, of liind-foot claws {sic, probably a misprint for hind 
foot with claws ) f inch. Pur dense, very soft, and fine; the surface fine greyish-brown on the upper parts; on 
the lower parts, feet and tail white, a little sullied; basal two-thirds or more of the upper fur dark slaty. 
“ Ears rounded, of medium size, rather oppressed.^ 
It is, I think, evident from the above, that Mr. Blyth based the distinction between his 
genus Phaiomys and Arvicola chiefly on the presence in the former of a claw to the rudimentary 
thumb; neither the general form nor the tail affording any distinctive character of importance. 
This claw is absent in some species of the genus Arvicola, but present, I think, in a 
still larger number. It is present, for instance, in the common water rat, A . amphibius ; Pallas 
mentions its existence in a more or less rudimentary form in A. socialist A. ceconomus, 3 A. 
gregalisf A. rutilusf and A. saxatilis, 6 it being very minute in A. gregalis and A. rutilus; 
whilst it is described as absent in A. alliarius? Its presence has, moreover, been noted in 
some Asiatic forms described in more recent works, as A. amurensis, 8 A. maximowicziif 
A. brandti , 10 A. obscurus f 1 and A. mandarinus , 12 and I note, in the first place, that these 
species belong to very different sections of the genus as distinguished by the characters 
of the teeth ; A. saxatilis and A. brandti, for instance, having, according to Milne-Edwards, 1:1 
one prism on the inner side of the last upper molars, in addition to those found in A. obscurus » 
A. mandarinus, u and many other species ; secondly, that careful and well-informed observers, 
with a wide knowledge of the genus, have not considered the presence or absence of a claw on 
the thumb a character of sufficient importance to justify its being used for generic distinction; 
and lastly, that there is an almost complete gradation from species wanting the claw to those 
which have it well developed, through forms in which it is more or less rudimentary. 
But if Phaiomys leucurus be relegated to the genus Arvicola, the name must be 
changed, as there is an A. leucurus of Gerbe, 15 described from the Alps of Provence in 
1 Evidently a misprint for lb. Theobald gives as the measurement of the total length 6T5 inches, of which the head was 1’30. 
and the tail T25. 
2 Glires, p. 220. 
3 lb., p. 234. 
4 lb., p. 244. 
5 lb., p. 248. 
6 lb., p. 256. 
7 lb., p. 253. 
8 Schrenk, Eeisen und Eorschungen im Amur-Lande, i, p. 129. 
9 lb., p. 140. 
10 Radde, Reisen im Suden von Ost-Siberien, i, p. 199, PI. VII, fig. 3. 
11 Eversman apud Middendorf, Sib. Reise, p. 109, PI. XI, figs. 1—5- Although the presence of the claw is not mentioned 
in the description, it is clearly shewn in figure 3 representing the skeleton. The original description of the species is in the 
Addenda ad cel. Pallasii Zoographiam, &c., fasc. 2,—a very rare book. 
12 A. Milne-Edwards, Rech. Mam. p. 129, P1. XII, XIII. 
13 Rech. Mam., p. 131. I have unfortunately been unable to consult a paper by Blasius on Arvicola, in the Munch, 
Gelerht. Anz., 1853, xxxvii, p. 105, as the volume is deficient in the only set in Calcutta, that belonging to the Asiatic Society. 
14 This character, I may note, appears quite as important as the presence of an additional ridge on the anterior upper molars, 
on the strength of which Hodgson’s genus Neodon has been established (Jerdon, Mammals, p. 216). The genus was originally 
proposed in the Annals and Magazine of Natural Histoiy for 1849, Ser. 2, Vol. Ill, p, 203, but it was not described, and 
it was merely said to differ from Arvicola in the character of the molars. The genus Neodon appears founded on characters of 
only specific importance, and the type, N. siklcimensis, is, I think, a true Arvicola. 
15 Rev. de Zool., iv, p. 260. 
L 
