PHANOPHILUS 75 
seen by fig. 42, is narrow and high. A single 
tooth measures 53 mm. from front to back, 
and 33 mm. in width. 
Specimen 3142 gen. and sp. ? 
This specimen is the mandible with the pared Ase Eternal 
milk dentition. The molars present suggest ““"" °”* 
Prosotherium triangulidens, but inc. 3 and the canine are 
present, and the first two incisors are not enlarged, so it 
would seem to represent a genus which I have not been 
able to identify. Molar 1 is bilobed and similar to that of 
Prosotherium. ‘The deciduous premolars are all present, all 
ee 
&, 
Fig. 44. Milk dentition, genus and species?—natural size. 
rooted, and all remarkable for their great antero-posterior 
elongation. Roots of the incisors and canine are present, 
that of the canine being the largest, and those of the incisors 
being about equal in size. This would suggest such a 
form as Protypotherium, were this genus represented in 
the Deseado beds. 
Interatheriidae 
The family is characterized by the incisors not being 
enlarged, by upper and lower premolars and molars being 
inflexed on both the inner and out sides, and by the inflated 
mastoid bulla being filled with cancellous tissue. The 
only genus referable to this family, from the Deseado 
beds, is Archaeophylus. 
Archaeophylus Ameghino 
Archaeophylus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 423. 
The genus is based on a skull which preserved most of 
the upper dentition except the incisors, and which shows 
the characteristics of the family in their inception. 
