ANATOMY OF THE BEAVER. 53 



entire ulna 4" 37'". The hands are small compared 

 with the feet. In the upper carpal row there are 

 two bones instead of the usual number of four. In 

 the second row a crescentic bone connects the thumb 

 with the lateral part of the head of the adjoining 

 (first) metacarpal. On the head of this metacarpal 

 are two smaller bones (trapezoids) overlying each 

 other, and articulating with the scaphoid of the first 

 row. On the third metacarpal is a wedge-shaped 

 bone with the apex toward the scaphoid. Next in 

 the row is a large bone (os magnum) receiving the 

 heads of th>e 4th and 5th metacarpals. The next 

 bone, occupying the position of the unciform, is large, 

 and is attached to the ulnar bone of the first row, 

 and supports the annular ligament. A third plate 

 bone, connected by ligament with the scaphoid, lies 

 over the root of the thumb and forms the other at- 

 tachment of the annular ligament. The phalanges 

 are normal, the thumb being very small. 



The pelvis is long; the lateral bones being 6" 50" 

 in length, and the ilia having but rudimentary alae. 

 The ischium and pubis are thin, and their expansion 

 is effected by the large thyroid foramen, 2" long and 

 1" broad, which is destitute of ligament. Between 

 the ischial tuberosities it is 3"; the transverse diameter 

 of the pelvis is 2". The greatest depth of the acetab- 

 ulum is superiorly and anteriorly in the line of the 

 ilium. There is the usual pit for the round ligament 

 which is well developed and strong, although R. 

 Wagner affirms that it does not exist in the mamma- 

 lia, except in man^ (i. p. 15). 



^ Elements of the Comparative Anatomy of the Vertebrate 

 Animals. By Rudolph Wagner. Transl. New York, 1845. 



