SINCLAIR : MARSUPIALIA OF THE SANTA CRUZ BEDS. 42 1 



The mandible is of the same depth as in Canolestes, with the lower 

 border approximately horizontal. Two conspicuous mental foramina are 

 present, situated respectively beneath the posterior premolar and the 

 anterior portion of the second molar. 



Halmarhiphus may be distinguished from Ccenolestes by the sharper 

 separation of the molar cusps, which in the latter are tending toward the 

 crescentic pattern of the Palaeothentinae. The molar crowns are less 

 quadrangular in outline and the metaconid on Mr is less reduced than in 

 Ccenolestes. More important differences would probably appear in the 

 upper dentition. Garzonia is readily separated from Halmarhiphus and 

 Ctznolestes by the single-rooted condition of Mi. 



HALMARHIPHUS NANUS Ameghino. 



(Plate LXIII, Figs. 9, ga ; Text Fig. 7.) 



Halmarhiphus nanus Amegh. ; Revista Argent, T. I, p. 308, 1891; 



fenum. Syn., p. 101, 1894; Bol. Ac. Cord., p. 357, 1894; Segundo 



Censo, etc., p. 187, 1898. 



The right half of a lower jaw of this little animal (No. 9593 American 

 Museum of Natural History) was collected by Mr. Barnum Brown on the 

 Rio Gallegos. Until a larger amount of material has been secured, the 

 generic and specific characters cannot be separately stated. The princi- 

 pal measurements are as follows : 



MEASUREMENTS. 

 Length of lower dental series from posterior border of alveolus of I T to M T 



inclusive ......... .008 



Length of antemolar series exclusive of I T . . . . . .003 



" " molar series . . . . . . . . -005 



Width of base of median incisor ..... .0008 



Depth " " .001 



Median premolar, antero-posterior diameter . . . .0012 



" " transverse "... .0005 



Posterior " antero-posterior " . . . -OOi 



transverse "... .0006 



M T , antero-posterior diameter . . . .0014 



" transverse "... - 001 



MJ-, antero-posterior " 



" transverse " - 0012 



M^, antero-posterior diameter . . . .0014 



" transverse " I 



