220 THE DESEADO FORMATION OF PATAGONIA 



and the molars small and buno-lophodont. From the 

 Deseado beds but one genus of this subdivision has been 

 found, Palaeothentes, designated by Ameghino first Epan- 

 orthus, then later Palaepanorthus, but as I can see no reason 

 for distinguishing the Deseado species of the genus from 

 those of the Santa Cruz, 1 have retained the name Palaeo- 

 thentes. 



The genera of this subfamily are distinguished as follows: 



Lower Third Premolar 



Palaeothentes 2-rooted, fairly large, equals pin. 4 in height. 

 Pilchenia 2-rooted, moderate size nearly equals pm. 4 in height. 

 Callomenus 2-rooted, small size much lower than pm. 4. 

 Decastris, i -rooted, vestigal. 



Palaeothentes (Moreno) Ameghino 



Palaeothentes Moreno, 1882, Patagonia, Resto de tin Continente hoy sub- 



mergido, p. 22, (nomen nudum). 

 Palaeothentes (Moreno) Ameghino, 1887, Enum. Sist. Espesies Mamif. Fos, 



Patagonia, p. 5. 

 Epanorthus Ameghino, 1889, Act. Acad. Nac. Cienc. Cordoba, t. 6, p. 271. 

 Epanorthus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 500. (nudum). 

 Palaepanorthus Amegh., 1901, Anal. Soc. Cienc. Argen., t. 51, p. 77, (nomen). 

 Palaepanorthus Amegh., 1902, Bol. Acad. Nac. Cienc. Cordoba, t. 18, p. 123. 

 Palaepanorthus Amegh., 1903, Anal. Mus. Nac. Buenos Aires, t. 9, (ser. 3, t. 



2) p. 239. 



Among the Santa Cruz specimens, this genus is distin- 

 guished by having in the lower jaw the large first incisor, 

 then five vestigal teeth, followed by a two-rooted, though 

 somewhat reduced, third premolar, next the enlarged 

 fourth premolar, making the sectorial tooth, and lastly 

 three buno-lophodont molars. 



There is considerable confusion as to the use of the gen- 

 eric name. Moreno designated the first specimen, Palaeo- 

 thentes, without a description; then Ameghino used this term 

 describing the species; later Ameghino thinking that the 

 name Palaeothentes was the same as Palaeothentis proposed 

 the name, Epanorthus, using this for the first description 



