352 



University of California Publications in Geology IT 0L - 7 



Measurements of Phalanx. No. ]9720 



Greatest length through middle of shaft 



Depth of proximal end 



Width of distal end 



73. mm. 



34.6 

 23.2 



MEGALONYX CALIFORNICUS, n. sp. 



Type specimen, a left humerus, no. 21003, Univ. Calif. Col. Vert. Palae., 

 from the asphalt deposits of Rancho La Brea. 



Paratypes: A left caleaneum, no. 20095; a third right metatarsal, no. 

 20001; various digital elements of anterior and posterior feet, nos. 20002- 

 20004 inclusive, Univ. Calif. Col. Vert. Palae., from the asphalt deposits 

 of Rancho La Brea. 



Diagnostic Characters of Species. — The material thus far 

 available represents a form somewhat smaller in size than 

 Megalonyx jeffersonii Desmarest. Head of humerus prominent, 

 two tuberosities farther separated than in M. jeffersonii; distal 

 trochlea wider than in M. jeffersonii, ulnar and radial facets of 

 equal width ; dorsal surface of tuberous apex of internal condyle 

 with short closed canal. Neck of caleaneum with relatively 

 greater vertical width than in M. jeffersonii; postero-inferior 

 extremity not decidedly directed to either outer or inner side. 

 Articulating surface of third metatarsal for cuneiform tridobed. 



Anterior Limb. — The head of the humerus, no. 21003 (fig. 12) 

 is more prominent in anterior view than in M. jeffersonii, due to 

 a wider separation of the two tuberosities. This separation in 

 M. calif or nic us resembles that of Nothrothcrium, but is not as 

 great as in Hapalops. The short and narrow bicipital groove 

 is distinct. The pectoral ridge, which is faintly indicated along 

 the upper half of the shaft, becomes prominent below the middle. 

 It is more distinct than in M. jeffersonii but less so than in 

 Mylodon. A slight projection occurs at the middle of the inner 

 border of the shaft. 



The "musculo-spiral course" is well defined laterally, the 

 dorsolateral margin differing from M. jeffersonii in protruding 

 slightly. A tendency toward a similar projection is seen in 

 Mylodon. The distal trochlea is relatively wider than in M. 

 jeffersonii, the ulnar and radial facets being of the same width 

 in M. calif ornicus, while in the former species the radial facet is 



