GLIRES OF THE SANTA CRUZ BEDS. 



391 



regard as dp- of this genus, although it is considerably larger than in 

 most individuals ; its relatively large size is due to the small degree of 

 abrasion which it has suffered, for it contracts much toward the base, 

 especially in the antero-posterior diameter. Dp T I have not found in so 

 early a stage and the youngest example is that shown in Plate LXV, 

 fig. 6 ; the tooth is still very large, but already has well developed roots ; 

 the grinding surface displays one wide and deep external fold and two 



FIG. 38. 



Skulls of Octodontidae, side view. a. Myocastor coy pus, x |. b. Capromys fournieri, x J. 



c. Neoreomys australis, x f . 



narrower and shallower internal folds ; in addition to these, the anterior 

 prism has two enamel lakes, of which the antero-external is larger and 

 crescentic in shape, and the postero-internal is very minute. 



As a whole, the dentition resembles that of Myocastor, though the molar 

 pattern is distinctly less complex ; that of Capromys is nearly as simple as 



