76 THE DESEADO FORMATION OF PATAGONIA 
Archaeophylus patrius Ameghino 
A. patrius Amegh., loc. cit. 
(oo BY, We found no specimen of this inter- 
>s esting type, but I give a diagram of 
Fig. 45. Archa hylus pa- 1: : z f K 
trius afer Ameghino, righ. Ameghino’s type, which shows the char- 
upper dentition—natural size. yee Space 
acteristics of the species and genus. 
The length of the premolar-molar series is 27 mm. 
Eutrachytheridae Ameghino 
The family consists of larger forms than the other fami- 
lies, and is characterized by the upper molars having the 
inflexion bifurcated, so that the teeth are at least incipiently 
three-lobed. [I would place in the family the genera, 
Eutrachytherus, Argyrohyrax, and Isopoedrium. 
Eutrachytherus Ameghino 
Trachytherus Amegh., 1889, Act. Acad. Nac. Cienc. Cordoba, t. VI, p. 918. 
Trachytherus Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 623. 
Eutrachytherus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 429. 
This genus was first called Trachytherus, and when this 
was found to be preoccupied, changed to Hutrachytherus. 
Ameghino gives the dental formula as ~77>, but in my 
specimen which is a comparatively young individual, | 
find a small alveolus for the upper canine, which modifies 
the formula to >~4 >. In the first upper dentition found, 
incisors 2 and 3 were represented by alveoli only, but our 
specimen shows these teeth, and we find that they have 
enamel only on the outer face, making this genus more 
specialized in this respect than any of the other typotheres. 
The upper molars have the deep inner inflexion bifurcated, 
which makes the tooth three-lobed, a character which 
grows more marked the older the individual is. The pre- 
maxillae are high and bring the snout well forward. The 
nasals are lacking, but the bounding bones show them to 
