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 1 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 £L. 
spegazzinianus. Each is covered with a layer of fully half 
a millimeter of cement. 
Fig. 49. E. grandis, molars of the left side—natural size. 
MEASUREMENTS 
Upper molar 1, length 29 mm., width 21 mm. 
Upper molar 2, length 303 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 1 is relatively somewhat 
wider than in the preceding genus. It seems to me that 
it is from such a genus that 7ypotherium arose, by the 
reduction of the lateral incisors, the canine, and the first 
