438 MILLER AND gidley: supergeneric groups of rodents 



Siibfamil}^ Rhizomyinae. — ^Like the Tachyorydinae but peculiarities of 

 infraorbital region carried farther, the neural notch being obliterated 

 and the foramen appearing as a small orifice confined to upper surface 

 of zygomatic root; teeth moderately hypsodont, the enamel pattern 

 obviously heptamerous or reduced-heptamerous and changing rapidly 

 during adult life. 



Rhizomys and related genera; Pliocene to Recent; southern Asia. 



Subfamily Br aminae.— Like the Rhizomyinae but cheekteeth with 

 definitely prismatic structure. 

 Bramus; Pleistocene; northern Africa (not seen). 



Family Spalacidae 



Like the Cricetidae but zygomasseteric structure unusual, the zygo- 

 matic plate narrowed and turned downward to a nearly horizontal posi- 

 tion, thus doing away with the separate neural portion of the opening 

 by a process the exact opposite to that bringing about a similar result 

 in some of the Rhizomyidae; skull excessively fossorial, the lambdoid 

 crest carried forward to level of zygomatic root. 



Subfamiy Myospalacinae. — Mandible scarcely movable at symphysis, 

 a large post-symphyseal buttress early developed; cheekteeth growing 

 from persistent pulps, the crowns elongated, the enamel pattern con- 

 sisting of alternating triangles, the posterior termination of m^ and 

 m^ rounded. 



Myospalax; Recent; Asia. 



Subfamily Spalacinae. — Mandible movable at symphysis through- 

 out life; cheekteeth moderately hypsodont, rooted, subterete, the pat- 

 tern reduced-heptamerous, changing rapidly with wear; skull with the 

 characters of the family carried to such an extreme as to make it the 

 most fossorial type known among rodents. 



Spalax, Recent, Prospalax, Upper Pliocene, and an undescribed genus 

 from the upper Oligocene; eastern Mediterranean Region, and southern 

 Europe. 



Family Muridae 



Skull as in the typical Cricetidae; cheekteeth f , the upper teeth with 

 a functional row of tubercles on lingual side of crown internal to the 

 protocone and hypocone, these tubercles entering conspicuously into the 

 plan of modification of the crowns. 



Subfamily Dendromyinae. — Upper cheekteeth with triserial arrange- 

 ment not fully developed; manus with only 3 functional digits. 

 The DenrfroA/iymae of authors; Recent; Africa. 



Subfamily Murinae. — Upper cheekteeth with fuU.y developed tri- 

 serial arrangement of tubercles always evident, though frequently vary- 



