^ll II 



i 1' 



I? ■■ 



S 1 





r)80 



MONOOItAPnS OF NORTH AMICUIOAN ItODKNTIA. 



wliich tlie close apposition of the iilnn and radius would indicate, the rela- 

 tions of thoir various articular surfiices arc tlie same as those in cases where 

 pronation and supination are perfect, and such movements are doubtless con- 

 siderable in extent. 



Manus. — The carpah are nine in number, in two rows, four in the proximal 

 and five in the distal series. The first bone of the proximal series, on the 

 radial side, develops a large, flat, falcate process as long as the Ist meta- 

 carpal, against which it lies ; this process supports the outer one of the two 

 large palmar tubercles at the radial side of the hand.* The second bone of 

 this series, lunare if not scapholunure, is also of great size, irregularly semi- 

 lunar in shape, with an oval convex facet, which forms most of the radio- 

 carpal articulation. The outer two bones are much smaller. In the distal 

 row, one of the five bones is probably an "os intermedium "; this and three of 

 the others are extremely small; the remaining larger bone is somewhat 

 uncinate. 



There are five metacarpals, of which the 1st is much shorter than the rest, 

 and directed obliquely away from them ; the others are approximately parallel ; 

 the ratio of their lengths is 3d, 4th, 2d, 5th, the last shortest. There is the 

 normal number of j)kalanges — two in the pollex, three in each of the other 

 digits. 



Pelvis. — The sacral portion of the pelvis has already been described 

 with the vertebrsE. The^/t'/« is rather long, narrow, and parallel-sided, about 

 two and a half inches long from apex of ilia to the opposite extremity. The 

 general axis of each innominate bone is straight. The ilia project about one- 

 fourth of their length in advance of the sae.um (which terminates oJ)po8ite the 

 posterior border of the iicetabula) ; their anterior prolongations embrace the 

 whole of the last lumbar vertebra. The ilia are narrow trihedral bones.curving 

 anteriorly outward, and somewhat clubbed at the extremity ; tlie edges are 

 all sharp, but the superior border is especially prominent ; the outer surface 

 is concave; the other two faces of the bone are flatter, the internal being 

 roughened for the sacro-iliac synchondrosis. The shaft of the bone is con- 

 stricted just above the acetabulum, though still markedly triangular in section. 

 The acetabula are deeply cupped, surrounded by a prominent rim, except 

 posteriorly, where the lip of the cup sinks into a deep notch. The ischial 



™* In the Beaver, there is said to be a liage " accessory " cvpal ossicle. It may be tbat the bona 

 hero (lescribi!!) is the lioniologons osKiulo of HaplodM, which, if siilistuntiatud, wonld furnish additional 

 evidence of aflinity lietweeu this genns and Cantor. 



