254 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
cles, as usual; the soles, on the contrary, only four—one long, lengthened, 
postero-internal, and three others at the bases of the 1st, 2d, and 4th—5th 
toes. The skin of the soles is not granular nor obviously reticulate, though 
it is crossed with lines in the dried state. The 1st toe is but little shorter 
than the 5th, the claw of which falls short of that of the 4th; this last is 
rather the longest, the 3d and 2d decreasing a little. The rudimentary thumb 
bears a claw; the other fore digits are subequal in length, and all long. As 
in many other aquatic mammals, the whole foot is set obliquely on the leg, so 
that its edge and not its surface may be opposed to the water in the forward 
movement of the member, and vice versd. The modification of the tail into 
the semblance and for the purpose of a rudder is the most remarkable fea- 
ture of the animal. This member is strongly flattened sideways in nearly all 
its extent, permitting readiest lateral flexion and but little up-and-down move- 
ment. The vertical width of the tail is increased by a fringe of stiffish hairs 
above and below; on the sides, the skin is almost naked, and cut into number- 
less scales, showing a disposition to form the rings so conspicuous in Mus ; 
but their annular allignment is not perfect, the general arrangement being 
nearer a quincunx. The ear does not show such development of the anti- 
tragus, or other mechanism for excluding water, as might have been antici- 
pated; but it is so small, so furry, and so deeply buried in the general pelage, 
that no additional contrivance is required. ‘The eye is very small; the muffle, 
completely furry except on the small nasal pads, is very obtuse, with thick 
fleshy lips, not cleft at the median septum; there are fleshy enlargements and 
hairy patches within, serving to diminish the oral aperture. ‘The whiskers 
are short, sparse, and stiff; there are other bristles over the eyes and under 
the chin. 
FIBER ZIBETHICUS, (L.) Cuv. 
Muskrat. 
Castor zibethicus, LINN., Syst. Nat. i, 1766, 79, no. 3 (quotes Brisson, Kalm, and Sarrazin).—ERxt., Syst. 
Reg. Anim. i, 1777, 444, no. 2.—Bopp., Elench. Anim. i, 1784, 166. 
Mus zibethicus, ScuREB., Siing. iv, ‘'1792”, 638, pl. 176.—GM., Syst. Nat. i, 1788, 125, no. 2 (quotes Schre- 
ber).—SHaw, Gen. Zool. ii, 1801, 44, pl. 129 (lower figure). 
Myocastor zibethicus, “ KERR’s Linnzeus, 1792”. 
Lemmus zibethicus, ‘FR. Cuy., Dict. Se. Nat. vi, 310, fig. —”.—Fiscu., Synop. 1829, 289, no. 1. 
Fiber zibethicus, Cuv., R. A. i, 1817, 192.—DxEsM., Mamm. ii, 1822, 279; Encye. Méth. pl. 67, f.6; Nouv. 
Dict. xxiii, 506.—SazB., Frankl. Journ. 659.—Hartan, Fn. Amer. 1825, 132.—GrirrirH, Anim. 
Kingda. v, 1827, 208.—GopMan, Am. Nat. Hist. ii, 2d ed. 1831, 58.—Rrcu., F. B. A. i, 1829, 115 
(describes black, white, and pied varieties).—DrKay, N. Y. Zool. i, 1842, 75, pl. 20, f. 2, pl. 
32, f. 3 (skull).—Scuinz, Syn. ii, 1845, 257.—Aup. & Bacu., Q. N. A. i, 1849, 108, pl. 13.— 
Kennicort, Agric. Rep. U. 8. Patent Office for 1856, 1857, 105, pl. 14.—Barrp, M. N. A. 1857, 
561.—Buterr, P. Z. 8. 1865, 682 (habits).—Cours, Proc. Acad. Nat. Sci. Phila. 1874, 196.— 
Cours & Yarrow, Zool. Expl. W. 100th Merid. 1876, —; and of authors generally. 
