SCOTAMYS 193 
of two laminae separated by a deep external fold, around 
the inner end of which the laminae are connected by a 
narrow bar. In the present condition of wear there is no 
indication of secondary furrows. The premolar is smaller 
than the molars. 
MEASUREMENTS SPECIMEN 3063 
Lower dentition, in. f to pm. 4 8 mm, 
Lower dentition, premolar 4 length 3 mm., width 2.5 mm. 
Lower dentition, molar 1 length 2.5 mm., width 2.5 mm. 
Lower dentition, molar 2, length 75 mm., width 3 mm, 
Height of mandible under pm. 4 5.5 mm. 
Fig. 126. Left mandible external side, x 4/1. 
Litodontomys gen. nov. 
One set of lower teeth found by the Amherst party 
shows a simplicity of pattern found in no other genus of 
South America; and this is, therefore, named Litodontomys. 
The teeth are brachydont, the premolar and the molars 
each being divided into two laminae by an external and 
an internal fold, the distinctive generic feature being in 
that this fold is narrowest at the margin of the tooth and 
expands internally. In connection with the expanded 
folds, the ends of the laminae are curved toward each other, 
so that in a worn specimen they would meet on the margins 
of the tooth, and leave the folds to appear as pits. No 
indication of a furrow is evident on either lamina. 
13 
