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 I, length 3 mm., width 2 mm. 



Lower dentition, molar 2, length 2.5 mm., width 2 mm. 



Lower dentition, molar 3, length 2 mm., width 1.75 mm. 



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 i in place. Pm. 3 is 



Fig. 147. Left mandible with premolar 3 

 to molar 2 4 times natural size. 



Fig. 148. Left mandible internal side 4 times 

 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. 



