1913] 



Stock: 



Nothrotherium and Megalonyx 



355 



the annular and index phalanges." 13 There is an equal possi- 

 bility that this is a second left digit of the posterior foot. 



No. 20003 belongs possibly to either the second or fourth digit 

 of the front foot. In the first phalanx there is no indication 

 of dorso-ventral curvature on the lateral faces of the proximal 

 end nor does the middle articulation narrow ventrally. An 

 offset occurs only on the inferior half of one side. The side 

 bordered proximally by the offset is distinctly narrower than 

 the opposite side. On the distal trochlear face, the condyle of 

 the shorter side widens inferiority. 



On the proximal articular face of the second phalanx the 

 surface articulating with the inferiorly broadened condyle of 

 the first phalanx is very slightly concave. The postero-dorsal 

 ligamental ridges are not prominent. The dorsal surface of the 

 smaller condyle is beveled laterally. 



Figs. 15 and 16. Megalonyx calif or nicus, n. sp. Left caleaneum, no. 

 20095, X V-t- Rancho La Brea Beds. Fig. 15, view of right side; fig. 16, 

 view of proximal end. 



Posterior Limb. — The left caleaneum, no. 20095 (figs. 15 and 

 16) agrees essentially with M. jeffersonii in its differences from 

 the caleaneum of M. sierrensis as described by Sinclair. 14 

 Important differences exist, however, between the Rancho La 

 Brea caleaneum and the caleaneum of M. jeffersonii. 



is Leidy, J., A Memoir on the Extinct Sloth Tribe of North America, 

 Smithson. Contrib. Knowl., vol. 7, p. 35, 1855. "Median phalanx" here 

 means the first phalanx of the median digit. 



" Sinclair, W. J., op. cit., pp. 158-159, pi. 22, figs. 2 and 3. 



