68 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



No. No. 



15436- 15,712. 



Metatarsal II, length 061 .059 



" " proximal width ........ .004 .004 



" " " thickness 010 .0095 



" " distal width 006 .006 



" " " thickness 0105 .0105 



Metatarsal III, length 075 



" " proximal width .019 



" " " thickness over hook ...... .021 



" " distal width 020 



Phalanx I, digit III, length . 037 .037 



" I, " " proximal width ....... .020 .020 



" I, " " " thickness 012 .012 



Phalanx 2, digit III, length .021 



" 2, " " proximal width . .0165 



Localities. — Ameghino gives no localities for P. principale or P. divor- 

 tium; the type of P. dichotomum was found at Mt. Observation. No. 

 15,732 was collected by Mr. Hatcher at Halliday's Ranch and No. 15,436 

 at Killik Aike. 



Proterotherium pyramidatum Ameghino. 



(Plate VIII, Fig. 5.) 



Proterotherium pyramidatum Amegh.; Enum. Synopt, etc., 1894, p. 37. 



As in the species of Licaphrium of the same name, the antero-internal 

 cusp (protocone) of m- is relatively large, flattened on the inner face and 

 of quite pyramidal shape ; there is no hypocone and the posterior cingulum 

 turns sharply forward at the inner angle, becoming continuous with the 

 sharp edge of the protocone. 



Among the casts sent to me by Dr. Ameghino are two specimens 

 referred to the present species. One of these (No. 9), the type, is a frag- 

 ment of the right maxillary with all three molars in place, and the other 

 (No. 10) has all of the grinding teeth of both upper and lower jaws, except 

 ms. Although both individuals conform to the definition of the species 

 as given above, there are some instructive differences between them in the 

 character of m-. In the type, that tooth is much reduced in size, the 

 antero-external border not overlapping the hinder margin of m- ; the two 

 external lobes are of nearly the same size and the posterior conule is 

 placed very near to the posterior cingulum. In No. 10, on the other 

 hand, m- is relatively larger and the anterior margin overlaps the hinder 



