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University of California Publications in Geology [Vol. 10 



fache iibertreffen. Bei Mylodon ist einerseits die Kralle des zweiten Fingers 

 nor halb so lang wie die des dritten, andererseits ist sie aber absolut kiirzer als 

 die entspreehende am Hinterfuss. 



In the light of the new interpretation here presented of digit 3, 

 pes of Mylodon, the ungual determined by Allen 17 as belonging to the 

 second digit of the manus of M. garmani should be regarded as of 

 digit 3, pes of that species. The ungual which has been determined 

 as of the third digit of the pes by Dr. Allen, 18 following Owen, belongs 

 to the second digit of the manus. 



Digits 4 and 5 have suffered the same amount of reduction in 

 M. harlani as in M. robust us. The first phalanx of digit 4 resembles 

 in size the corresponding phalanx of digit 3, but differs greatly from 

 the latter in general shape and in the nature of the proximal and distal 

 articulating faces. The proximal face presents a vertical concavity 

 to conform with the distal end of the metatarsal. Bordering the 

 lower half of the inner margin of the proximal concavity and con- 

 fluent with it is an articulating offset. The ventral margin of the 

 phalanx below the concavity is notched and bears on each side a small 

 facet for a sesamoid. The distal articulating face has been shifted 

 inward, causing the first phalanx to be decidedly oblique with reference 

 to a median vertical plane. This surface is concave transversely and 

 of greatest depth along the inner side. Accompanying the obliquity 

 of the phalanx is the greater length of the outer side, which is twice 

 that of the inner. 



The fifth metatarsal in M. harlani bore at the distal end a nodular 

 rudiment, which in turn articulated distally with a much smaller 

 element, as in M. robust us. 



Comparison With Other Mylodont Genera 

 In the following comparison of the pes of Mylodon harlani with 

 that of other mylodont genera, it is desired at present only to indicate 

 such of the contrasting features as may be seen in the complete foot- 

 structure of these forms. The comparative study of the pes of 

 Lestoclon armatus by Gervais 10 has been of much value in this con- 

 nection, while the description of the foot-structure in Scelidotheriuni 



i- Allen, G. M., op. cit., p. 336, pi. 3, fig. 9. 



is Ibid., p. 340, pi. 3, fig. 12. This interpretation of the unguals of M. garmani 

 is also held by Mr. J. Z. Gilbert. 



1 » Gervais, P., Memoire sur plusieurs especes de mammiferes fossiles propres 

 a l'Amerique Meridionale, Mem. Soe. Geol. France, Ser. 2, T. 9, Mem. 5, pp. 21-35, 

 pis. 5-7 (pis. 25-27), 1873. 



