RODENTIA-ARVICOLINAE—FIBER ZIBETHICUS. 
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FIBER ZIBETHICUS. 
Musk Rat. 
Castor zibelhictis, Linn. Syst. Nat. I, 1766, 79. 
Erxleben, Syst. 1777, 444. 
Boddaert, El. Anim. I, 1784, 166. 
Pallas, Zoog. Rosso-Asiat. I, 144. 
Mus zibethicus, Gmelin, Syst. Nat. I, 1788, 125. 
Schrebek, Saugt. IY, 1792, 638; tab. clxxvi. (Ondatra in text.) 
Shaw, Gen. Zool. Mamm. II, 1801, 44; pi. cxxix. 
Myocastor zibethicus, 1 Kerr’s Linnaeus, 1792. 
Fiber zibethicus, Cuvier, R. A. I, 1817, 192. 
Desmarest, Mamm. II, 1822, 279. 
Harlan, F. Am. 1825, 132. 
Griff. Cuv. Y, 1827, 208. 
Richardson, F. B. A. I, 1829, 115. 
Dekax, N. Y. Zool. I, 1842, 75; pi. xx, fig. 2 ; pi. xxxii, fig. 3. (Skull.) 
Aud. & Bach. N. Am. Quad. I, 1849, 108 ; pi. xiii. 
Kennicott, Agric. Rep. U. S. Pat. Off. for 1856, (1857) ; plate xiv. 
Lrnmus zibethicus, Fischer, Synopsis, 1829, 289. 
Ondatra zibethicus, Waterhouse, Charlesw. Mag. N. H. Ill, 1839, 594, (fig. of skull.) 
Musk beaver, Pennant, Hist. Quad. 1781, No. 252.—In. Arctic Zool. I, 1784, 106. (Leverian Museum.) 
Body thick and clumsy ; in shape resembling the arvicolas. Neck indistinguishable. Feet 
moderately large. Tail about equal to the body without the head. 
Head broad, depressed, acute. Eye very small; its long diameter not equal to the width of the 
two upper incisors ; its centre about midway between the tip of the nose and the posterior mar¬ 
gin of the ear. The ear is quite small; nearly as broad as high : truncate and rounded above; 
there is no distinct tragus, the cartilage being entirely straight in this region. The antitragus 
is, however, quite prominent, as a rectangular projection at the bottom of the external ear; there 
does not appear to be any natural arrangement in the ear to exclude water, hut the dense fur 
with which both sides are coated, and completely concealing it, answers the same purpose. 
The external surface of the outer ear, however, is only hairy near the upper margin posteriorly, 
leaving the rest of this surface to the anterior edge of the ear, and around and above the meatus, 
entirely naked. The septum of the nostrils is thick, as wide as the upper incisors, and is 
marked longitudinally by a broad shallow groove. There is a small papilla on the posterior 
edge of the nostril which may serve as a valve to close it under water. The upper lip is not 
split, hut is hairy between the incisors and the nose. The lips are thick and fleshy, the upper 
covered with hair a little within the margin. On each side of the upper lip there is an internal 
projecting flap, which, when the two are brought together, completely overlap and conceal the 
anterior portion of the palate, and reducing the opening of the mouth to a square aperture. 
There are somewhat similar flaps on the lower lip folding over the base of the incisors. On 
the inside of the upper lip, again, and placed behind the flaps above mentioned, is a square 
patch of stiff hairs pointing backwards and inwards, and when the flaps are brought together, as 
above described, are in contact with each other, and serve to diminish the size of the free open¬ 
ing of the inner mouth; these patches are completely isolated from all the other hairs. There 
'The genus was established for Myopotamus coypus— should not Kerr’s name take precedence for this? 
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