MERRIAM: THE FAUNA OP RANCHO LA BREA. 237 



tinguished from that of the timber wolves by any sharply-marked characters. 

 The head of the radius is, in general, relatively thick anteroposteriorly in cor- 

 respondence to the anteroposterior thickness of the massive distal end of the 

 humerus. On the distal end of the radius there is commonly only a faint groove 

 for the tendon of the extensor ossis metacarpi pollicis, whereas in many modern 

 wolves and coyotes this groove and the tubercle above it are clearly 

 marked. The small size of the groove possibly indicates weakness of the extensor 

 muscle of the thumb. A similarly shallow groove has been noted on one radius 

 of a specimen of G. occidentalis. 



Study of a large series of specimens of C. dirus indicates that the feet 

 are not relatively as heavy as in the large timber wolf, G. pambasileus. The 

 mesopodial elements of the average specimens are of about the same size 

 as those of a specimen of G. pambasileus in which the skull is somewhat smaller 

 than in the average of G. dints. Compared with the same skeleton of C. pam- 

 basileus, the average specimen of G. dims has absolutely smaller metapodial 

 and phalangeal elements. 



In the mantis of G. dirus, excepting minor differences, -the form of the 

 elements generally resembles that of the modern wolves quite closely. Among 

 the carpals, the scapholunar seems commonly to be distinguished by the shorter 

 transverse diameter of the medial facet of the distal side upon which the 

 trapezoid articulates. This would seem to indicate a smaller transverse diam- 

 eter of the trapezoid and a corresponding narrowing of the head of metacarpal 

 two. It has not, however, been noted that either of these elements is markedly 

 narrowed. The metacarpals in some cases have the shaft relatively wide 

 anteroposteriorly in G. dirus. In metacarpal four the anterior medial facet at 

 the proximal end is developed as a relatively long downwardly extended surface 

 marked by a gentle elevation at about the middle of its length. In G. pam- 

 basileus this facet is shorter vertically, and the protuberance is much more 

 prominent. In some of the other canid forms, as in the domestic dog and in the 

 coyote, this facet does not reach as far down on the shaft. 



So far as can be determined, the pollex is not larger, and is probably on the 

 average smaller, than in the timber wolves. The finding of skeletons in which 

 the elements are associated is very uncommon at Rancho La Brea, and it has 

 been especially difficult to make certain of the association of the smaller ele- 

 ments of the limbs. The suggestion that the pollex was small is based on the 

 fact that the average of the specimens of metacarpal one in the collection is 

 relatively small, this evidence being supported by that of the small groove for 

 the tendon of the extensor ossis metacarpi pollicis, and the small, short facet 

 for the trapezoid. 



The average of the phalangeal elements of the anterior limb in the collec- 

 tion is smaller than in a large specimen of G. pambasileus. The terminal phal- 



