82 



THE DESEADO FORMATION OF PATAGONIA 



Eutrachytherus conturbatus Ameghino 



Trachytherus conturbatus Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 623. 

 Eutrachytherus conturbatus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 

 429. 



This species is founded on upper teeth, which are said 

 to be relatively smaller anteriorly, and actually smaller 

 throughout, by about 15% than are those of the preceding 

 species. Molar I measures 17 mm. long by 9 mm. wide. 



Eutrachytherus grandis sp. nov. 

 This species is based on upper molars I and 2 of the 



left side, from the Deseado beds, of the Chico del Chubut, 



west of Puerto Visser. 

 The teeth are typically 

 those of the genus and 

 differ only from other 

 species in their large 

 size, being some 50% 

 larger than the corre- 

 sponding teeth of E. 



spegazzinianus. Each is covered with a layer of fully half 



a millimeter of cement. 



MEASUREMENTS 



Upper molar I, length 29 mm., width 21 mm. 

 Upper molar 2, length 30^ mm., width 18 mm. 



Argyrohyrax Ameghino 



Argyrohyrax Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 435. 



The genus is distinguished by the full dentition in closed 

 series, and by the upper molars having a deep internal 

 inflexion which is bifurcated, making the teeth at least 

 incipiently three-lobed. Incisor I is relatively somewhat 

 wider than in the preceding genus. It seems to me that 

 it is from such a genus that Typotherium arose, by the 

 reduction of the lateral incisors, the canine, and the first 



Hi' 



Fig. 49. E. grandis, molars of the left side natural size. 



