SINCLAIR: MARSUPIALIA OF THE SANTA CRUZ BEDS. 431 



No. 15,225. No. 15,925. No. 9550. 



Posterior premolar, an tero- posterior diameter. .0043 .004 .004 



transverse diameter . .0023 .0022 .0022 



M-L, antero-posterior diameter . . . .004 .0038 .004 



" transverse " ... .0032 .003 -0033 



M^, antero-posterior " ... .0025 .0025 .0028 



" transverse " ... .0032 .003 .0033 



Mi, antero-posterior " ... .0017 .0018 



" transverse " ... .002 .002 



MA ( antero-posterior " ... .001 .001 



" transverse " ... .0013 .0012 



Greatest interorbital width .... .0105 

 Least width of brain-case .... .007 

 Greatest breadth of nasals .... .0087 

 Depth of skull to alveolar border at front of 



orbit 012 



Width of palate between anterior premolars . .007 



" " " at Ml oio 



" " " " M oio 



PAL^EOTHENTES LEPIDUS Ameghino. 



(Plate LXII, Figs. 6, 6a.) 



EpanorthTis lepidtis Amegh. ; Revista Argentina, I, p. 305, 1891. 



This species, is known only from the mandible, of which the American 

 Museum collection contains four incomplete specimens (Nos. 9596-9598, 

 9600) found by Mr. Brown on the Rio Gallegos. 



In size P. lepidus is intermediate between P. minutus and P. interme- 

 dius. The vestigial teeth occupy a shorter space than in P. minutus and 

 are more closely crowded. The alveoli of the first and second are larger 

 than those of the third and fourth, are closely adjacent and strongly 

 inclined forward. The alveoli of the third and fourth vestigial teeth are 

 approximately vertical. 



The mental foramina vary considerably in size and relative position and 

 are of little diagnostic value. The principal measurements agree closely 

 with those of a natural-size photograph of the type in the Ameghino col- 

 lection, and have been depended on largely for the correctness of the 

 specific identification. 



