140 MEDICAL ZOOLOGY. 



Characters. A double claw on second hind toe. Hind feet webbed. Tail 

 broad, flat and scaly. Molars - , complicated or folded, with one groove 



on the inner side of each upper molar, and three on the outer, and vice versa 

 below; the anterior molars sometimes with more. (Baird.) 



C. canadensis, Kuhl. Head large and broad ; nussle naked ; nostrils 

 lateral, subcrescentic. Upper lip acutely emarginated, though scarcely bifid. 

 Eyes small, placed midway between the end of the snout and the auditory 

 aperture. Ears of moderate size (infra), thick and nearly orbicular, densely 

 covered with hair on both surfaces. Limbs large and stout; the under surfaces 

 of all the feet entirely naked; the upper surfaces coated with short, stiff silky 

 hairs ; the fore claws are about as large as hinder ones. Front foot with five 

 distinct fingers, each armed with curved, rounded claw ; third finger longest, 

 the fourth a little shorter ; then in order to second and fifth; the claw of the 

 first reaches as far as the cleft between the third and fourth. The claw of 

 second toe possesses a claw-like appendage. There are only two tubercles on 

 the palm, both large, and placed side by side ; the exterior twice as large as 

 the interior, and extending further back. Hind feet large, their plane ob- 

 lique to body. Toes connected by thickened naked web extending between 

 their tips. In walking the whole plantar surface touches the ground. Tail 

 conical at base, where it is densely covered with hair, but suddenly becomes 

 very flat and depressed. It is for the greater part covered with transversely 

 elongated subhexagonal scales arranged in quincum with tolerable regularity 

 on each side. Short downy hairs project between the scales, obscuring but 

 not concealing them. Fur of two kinds; upper and longer hair coarse, 

 smooth, and glossy ; under coat dense, smooth, and silky. Usual color red- 

 dish brown; on back of a shiny chestnut color ; on the under surface and 

 around mouth and throat, a shade lighter ; sometimes quite dark, and again 

 of rather a light yellowish tint of the same. (Baird.) 



Skull. Facial portion but little smaller than brain-case, narrow between 

 the eyes. Incisive foramina long and narrow, occupying rather less than 

 one- third of interval between incisors and molars. Zygomatic arches bold, 

 thicker in centre than toward extremities. The infraorbital foramen a small 

 slit, gives no transmission to muscle ; not seen from the side. Ext. auditory 

 passage, a well-pronounced tube, directed forward and outward. The lower 

 jaw with articular surface broadly oval, the coronoid process thick, angle 

 broad and rounded. (Wagner's Schreber.) 



Teeth. Line of upper molars decidedly convergent. Palate hollowed out 

 between incisors and molars. Inner side of upper molar with one -groove, 

 the outer three; this being reversed in the lower jaw, which shows four 

 grooves on the inner side. The anterior molars in both jaws are largest, the 

 rest diminishing backward very gradually; the anterior molar is, however, 

 longer, proportionally, than the corresponding upper one, and the lower line 

 of molars exceeds considerably the upper. (Baird.) 



Cervical vertebrae, 7; dorsal, 14 ; lumbar, 5; sacral, 4 ; caudal 28. Thorax 



