30 THE DESEADO FORMATION OF PATAGONIA 



LITOPTERNA 



This order of South American ungulates is less abun- 

 dantly represented in the Deseado formation than in the 

 Santa Cruz, but most of the genera of this latter formation 

 have representatives in the Deseado so that they seem to 

 have diverged still earlier. 



By Scott the order is divided into two families, the 

 Proterotheriidae and the Macrauchenidae, the less known 

 Adiantidac being placed under the latter family until 

 better known. 1 feel that I should prefer to retain the 

 Adiantidac for the present, until they can be shown to be 

 subordinate to another family, so that in this paper the 

 three families are retained. The striking features of the 

 two larger families may be best brought out by a compari- 

 son of their chief features as follows. 



Proterotheriidae Macrauchenidae 



Upper inc. 2 and lower inc. 3 enlarged Incisors, canine, and premolar I 



and tush-like, growing from per- simple, compressed, subequal in 



sistent pulps. size, and rooted. 



Nasals normal Nasals shortened indicating a pro- 



boscis. 



\'c< k short. Neck long. 



Feet with median digit enlarged, lat- Feet with all three digits subequal in 



eral digits reduced. size. 



Proterotheriidae Ameghino 



In the Deseado, this family is scantily represented as 

 compared with the rich fauna, both as to species and num- 

 bers of individuals in the Santa On/, but of the four chief 

 genera of the Santa Cruz, three have been found, though 

 the remains are very fragmentary. They are the genera 

 Eoprototherium, belonging to the Prototherium series, 

 D ciiler other ium belonging to the Thaotherium series, and 

 Notodiaphorus representing the Diadiaphoms series. 



