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University of California Publications in Geology [Vol. 10 



concave above. The distal articulation is elongate dorsoventrally, con- 

 vex, and faces upward and slightly inward. The lower margin of the 

 surface is straight. The inner side of the metatarsal is convex dorso- 

 ventrally, while the outer side, as in M. robustus, bears a narrow 

 vertical groove, which joins below an excavation between the proximal 

 and distal extremities. 



A single specimen, no. 22772, representing a fusion of the middle 

 cuneiform and metatarsal 2 in the pes of M. harlani, occurs in the 

 collections at the University of California from the asphalt beds. All 

 indications of an original separation are obliterated, although the two 

 elements are easily recognized by their otherwise characteristic shape 

 (contrast tigs. 3(7, 3b, and 4a, 46). Along the proximal margin of 

 the outer side in no. 22772 there is no distinct facet for the external 

 cuneiform. The specimen is of special interest in its great similarity 

 to Owen's figure and description of metatarsal 2 of M. robustus. 7 It 

 suggests, at least, that in the latter species the second metatarsal as 

 determined by Owen may possibly be the homologue of no. 22772 from 

 Rancho La Brea. 8 



In M. harlani the third metatarsal articulates with more of the 

 oblique proximal face of metatarsal 4 than in M. robustus, reaching 

 half way across this face. The fourth metatarsal may be slightly 

 longer than in the South American species. In the fifth metatarsal 

 the large and heavy lateral process of the proximal end is well formed. 

 It projects outward and backward more from the side of the meta- 

 tarsal than in M. robust us, resembling in this respect Scelidotherium. 

 M. harlani further agrees with the latter genus and differs from M. 

 robustus in that the fifth metatarsal does not touch the calcaneum. 

 It is possible, however, that in M. robustus some of these characters 

 may be subject to intraspecific variation. 



Digits. — Mylexlon harlani agrees with its South American contem- 

 porary in the loss of the first digit, the presence of claws on digits 2 

 and 3, and the amount of reduction suffered by the fourth and fifth 

 digits. 



The second digit, as in M. robustus, consists of two elements. 



i Owen, R., op. cit., pis. 21 and 22. See also his description quoted above. 



8 Dr. W. D. Matthew, who very kindly examined for the writer the mylodont 

 foot material in the American Museum of Natural History, states that the 

 middle cuneiform in the feet of Mylodon in which it is preserved is much shorter 

 than the second metatarsal. In this respect the second metatarsal agrees with 

 Owen 's figure, but the middle cuneiform appears to have a different shape. 

 Dr. Matthew notes further that in the specimen of Lestodon the middle cunei- 

 form and second metatarsal are co-ossified. 



