HAMILTON: HETEROCEPHALUS, AFRICAN BURROWING RODENT. I// 
The slender clavicle is lO mm. It articulates with the acromial 
process and is somewhat flattened at this point. The clavicle passes 
medially, curving twice before it ends in the rounded sternal termination. 
Anterior Liaib. 
Humerus. The humerus, u mm. in length, articulates with the 
scapula at the glenoid cavity and the radius and ulna distally. This bone 
is flattened in a cephalo-caudad direction. A well-developed deltoid crest 
is present. The trochlea and the capitellum are of the same size. 
Ulna. The ulna measures 12.5 mm. in length and curves toward the 
head. The greater sigmoid cavity receives the distal portion of the 
humerus. From here the olecranon process extends proximally for 3 mm. 
The radius is 8.6 mm. in length and lies rather closely applied against 
the ulna. For half its length there is a space between it and the ulna. 
This is quite dift'erent from the situation found in the specimen studied 
by Parona and Cattaneo, where the two bones are so closely applied as 
to leave no room between them. The distal extremities of the radius 
and ulna are of the same size. 
Hand. The bones of the carpus number six, and are closely joined 
by ligaments. Five slender metacarpals occur. The pollex is the short- 
est, this bone measuring only 1.5 mm. Next in length is the fifth, which 
is 2 mm. The second and fourtb measure 4 mm., while the longest, the 
third, measures 5 mm. 
Digits. The pollex has two phalanges, the remaining four have three 
each. Each digit possesses a minute nail. The first and fifth are 4 mm., 
the fourth is 6 mm., while the second and third are 7 mm. and 8 mm. 
respectively. 
Pelvic Girdle. 
The pelvic girdle is formed by the two innominate bones. These are 
joined to the first and second sacral vertebra. The bones of the pelvic 
girdle are so tightly fused that the sutures cannot be determined. The 
figure shows the general shape of this structure better than a written 
description. 
Posterior Limb. 
The femur is 13 mm. in length, flattened in a cephalo-caudad direction. 
The head, situated on the medial side, articulates with the acetabulum. 
The neck is not noticeably constricted. The greater trochanter is very 
distinct, but does not reach to the height of the articular head. It repre- 
