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, I have retained the name Palaeo- 
thentes. 
The genera of this subfamily are distinguished as follows: 
Lower THIRD PREMOLAR 
Palaeothentes 2-rooted, fairly large, equals pm. 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, 1-rooted, vestigal. 
Palaeothentes (Moreno) Ameghino 
Palaeothentes Moreno, 1882, Patagonia, Resto de un 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 
