7 6 THE DESK ADO FORMATION OF PATAGONIA 



Archaeophylus patrius Ameghino 



A. patrius Amegh., loc. cit. 



We found no specimen of this inter- 

 esting type, but I give a diagram of 

 Ameghino's type, which shows the char- 



upper dentition natural size. . c .-, * 



actenstics 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 Eutrachytherus. 

 Ameghino gives the dental formula as - 2 ^ * , but in my 

 specimen which is a comparatively young individual, I 

 find a small alveolus for the upper canine, which modifies 

 the formula to \ [ ^ . 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 



