1903.] Matthew^ Fauna of Titanotheriutn Beds of Montajia. 2 I 5 



M* transverse 2.5 mm. 



" longitudinal 1.8 



M3 transverse 2.3 



" longitudinal 2.0 



Width of palate, including molars 9.6 



? HETEROMYID.'E. 



Gymnoptychus minor (Douglas). 

 Euniys minor Douglas, Trans. Am. Phil. Soc. 1901, 16. 



The position of Gymnoptychus and Heliscomys has been 

 variously given by different authors; they are, in fact, rather 

 remote relatives of any modern type, and combine charac- 

 ters of Sciuridae, Geomyidag, and Heteromyidae with others 

 peculiar to themselves or shared by the Ischyromyidae. The 

 dental pattern strongly suggests that of Ischyromys, but the 

 resemblance maybe superficial; by simplification and hypso- 

 donty it might be 

 converted into a 

 Heteromy id pattern . 

 I place the genus in 

 this family on Scott 's 

 authority. ,^ L j, ;. 



The present spe- b ,,— -?=J 1 \ V 



cies is intermediate 



in size between G. (/^ •^*f~^^"^^^^^A£^JcC-'^} 

 minutns and G. liolo- 

 phits, but nearer to 



Fig. 10. Gymnoptychus minor. Lower jaws, four times 

 the latter. The type natural size. ^HI , external view, No. 9632 ; 5, crown view of 

 teeth, No. 9630. 



of G. iioLopniis re- 

 tains the milk dentition; a specimen of G. minor of corre- 

 sponding age shows a smaller and shorter d^ and somewhat 

 narrower and smaller nii. 



Seven lower jaws are referred to this species. 



Measurements. 



Type (Douglas). No. 9630. 



Lower dentition p4-m3 5.5 mm. 



molars mi-m, 4-° 



P4 transverse i .3 mm. i .3 



" longitudinal 1.5 1.4 



Mi transverse 1.7 i-7 



" longitudinal 1.5 1-4 



Diastema behind incisor 4-3 



