EDENTATA OF THE SANTA CRUZ BEDS. f 265 



MEASUREMENTS. 



Upper dentition, length 069 A, length 008 



-& 038 " width 012 



i, length (i. e., antero-posterior diameter) .008 &-, length 006 



" width (i. e., transverse diameter) 006 " width oio 



^, length 009 Palate width at 1 025 



"width 012 i 015 



, length 0085 " "*- 014 



" width 013 Muzzle, width over J- 042 



EUCHOLOEOPS Ameghino. 



(Plates LV-LVII.) 



Eitcholccops Amegh.; Enumeracion sistematica, etc., 1887, p. 21. 



This genus is nearly allied to Hapalops, which it resembles in all parts 

 of the skeleton, the constant differences between the two genera being 

 almost confined to the dentition and skull. Specimens of Eucholczops are 

 very much less common in the Santa Cruz beds than those of Hapalops 

 and there is no such abundance of species as in the latter, but we meet 

 with the same variability and the same difficulty in making any satisfac- 

 tory systematic arrangement. 



In the dentition, the characteristic feature of the genus is to be found 

 in the first tooth of each jaw, which is large, prominent and caniniform, 

 usually pointed by abrasion and placed externally to the line of the other 

 teeth. Some individuals show signs of what may be sexual differences in 

 the size of these teeth, which are considerably larger in certain specimens 

 than in others which differ from the former in no other respect; i is 

 implanted close to the anterior border of the maxillary and is always fol- 

 lowed by a relatively long diastema. The molariform teeth resemble 

 those of Hapalops in shape, being transversely oval or obscurely rectangu- 

 lar and grooved by a deep valley. 



The skull has a similar general appearance to that of Hapalops, but 

 with a number of constant and characteristic differences ; it is shorter in 

 proportion and quite conspicuously broad and heavy; the sagittal and 

 occipital crests are much better developed and in some of the species are 

 very prominent, less so in others, and the supraoccipital is little or not at 

 all reflected over upon the dorsal side of the cranium. The muzzle is 

 very broad, expanding anteriorly and, except for the premaxillae, abruptly 

 truncated ; the facial portion of the maxillary is not continued in front of 



