EDENTATA OF THE SANTA CRUZ BEDS. 269 



EUCHOLCEOPS EXTERNUS Ameghino. 



(Plate LVI, Fig. i.) 



Eucholceops extemus Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, 



p. 322. 



The type-specimen is a finely preserved skull and mandible in the 

 Ameghino collection and, if its peculiarities are not abnormal, the species 

 is well distinguished. The principal characteristic is given by the shape 

 of the caniniform teeth, which are very large and indicate that the animal 

 was a male ; the lower one bites inside of the upper one, instead of be- 

 hind it, and thus its abraded surface presents outward, not forward as it 

 does in almost all other known Santa Cruz Gravigrada ; similarly the 

 worn surface of - is internal, not posterior. The dimensions of this speci- 

 men are as follows and show that this species is considerably smaller than 



the preceding one. 



MEASUREMENTS. 



Upper dentition, length 060 Lower dentition, length 048 



" diastema, length 019 Skull, length condyle to anterior nares. .148 



EUCHOLCEOPS PRONTO Ameghino. 



(Plates LV; LVI, Figs. 2-4 a ; LVII, Fig. I.) 



E^tct^ol(Eops fronto Amegh. ; Rev. Argent. deHist. Nat., T. I, 1891, p. 322. 

 E^lcholo^ops latifrons Mercerat ; Rev. del Mus. de La Plata, T. II, 1891, p. 15. 

 Eucholaops lafonei Mercerat ; Ibid, p. 16. 



, The following description is founded upon the types of Ameghino and 

 Mercerat, upon an incomplete skull, with mandible and several bones of 

 the skeleton (No. 9,241) in the American Museum of Natural History, 

 and a second mandible (No. 9,575) in the same collection, and upon a 

 mandible and several vertebrae (No. 15,314) in the Princeton Museum. 

 The dimensions, though variable, are much less than those of E. ingens. 

 The teeth vary considerably in size and shape, apparently even in indi- 

 viduals of the same sex. In the supposed females the caniniforms are 

 quite small and in the type of E. latifrons Mercerat (figured by Lydekker, 

 '94, PI. LIX, fig. 4; LX, i) which is probably a young female, the 

 upper caniniform is very small, laterally compressed and projecting rela- 

 tively little beyond the line of the upper teeth, and of a shape resembling 

 that seen in Hapalops. In the males the caniniforms are large, trihedral 

 and pointed by wear, similar to those of E. ingens in shape, but some- 



