ANATOMY OF THE BEAVER. 51 



the fourth ; then the second and the fifth. Between 

 the third and fourth fingers is a rudimentary web, ex- 

 tending to the second plialanx, measuring on its edge 

 60'". The foot is Qi to 7" long. The upper surface is 

 covered with short silky hairs. Below it is naked. At 

 the base of the first toe is a tubercle. The third toe is 

 the longest; then in order of length the fourth, second, 

 fifth, and first. The claws are larger than those of 

 the hand, the third claw measuring from 87'" to 1" 10'" 

 in length, and 34'" to 38'" in width. 

 There is an extra flattened claw lying ^^^' ^' 



under the regular claw of the second 

 toe (Fig. 2) . All the toes are connect- 

 ed, to their extremities, by a firm naked 



I 1 ... insiue view 01 aouDie 



web or membrane, measurmar on its , 



' o claws. 



margin, when the toes are spread, 7i 

 to 8i inches. The beaver has four nipples, two be- 

 tween the shoulders, 3" apart, and two, 3" farther 

 back, 4" apart. 



OSTEOLOGY. 



The skeleton of the beaver, of which a representa- 

 tion is given PI. III., affords 273 bones, including the 

 aural ossicles and excluding the sesamoid bones. Of 

 these there are 38 of the head, 20 teeth, and 215 

 bones of the trunk, tail, and extremities. The beaver 

 has 55 vertebrae, viz., cervical, 7; dorsal, 14; lumbar, 

 5; sacral, confluent, 4; and caudal, 25. 



The first and second cervical vertebrae are strong, 

 the second and third are the smallest. Six have for- 

 amina for the vertebral artery. The head of the first 

 rib is articulated between the bodies of the seventh 

 cervical and the first dorsal. The last four lumbar 



