CALLOMENUS 223 
SPECIMEN No. 3110 
Lower dentition, distance from premolar 3 to molar 3 14 mm. 
Lower dentition, premolar 3, length 2 mm., width .75 mm. 
Lower dentition, premolar 4, length 5 mm., width 2.5 mm. 
Lower dentition, molar 1, length 3 mm., width 2 mine 
Lower dentition, molar 2, length 2.5 mm., width 2 mm. 
Lower dentition, molar 3, length 2 mm., width 1.75 mim. 
Lower dentition, height under pm. 4 5 mm. 
Callomenus Ameghino 
Callomenus Amegh., 1891, Neuvos Restos Mamif. Fos. Patagonia Austral, p. 
20. 
Callomenus Sinclair, 1901-6 Princeton Patag. Expeditions, vol. 4, p. 434. 
This genus has not been previously reported from the 
Deseado beds, but we found a tiny lower jaw with three 
teeth to represent it. The genus is distinguished by pre- 
molar 3 being two-rooted, but so small as not to attain the 
height of premolar 4. 
Callomenus praecursor sp. nov. 
The type is specimen No. 3020, a fragmentary mandible 
with premolars 3 and 4 and molar 1 in place. Pm. 3 is 
Fig. 147. Left mandible with premolar 3 Fig. 148. Left mandible internal side—4 times 
to molar 2—4 times natural size. natural size. 
two-rooted, but so small as to be entirely overshadowed 
by the succeeding pm. 4, hardly reaching a half the height 
of that tooth. On the last premolar and the first molar, 
the cusps are arranged in a trigonid in front and a talonid 
behind, the cusps being joined by thick ridges, making two 
connecting crescents. 
