26 MANUAL OF NATURAL HISTORY. 



molars, which have flat or blunt tuberculated crowns ; 

 eyes large and lateral. 



1. Family. — Squirrels (Sciuridse). Head rather 



broad ; eyes large and prominent ; fore feet 

 with four toes, hind five; tail more or less 

 lengthened, generally very hairy and ex- 

 panded in the arboreal species, bushy in the 

 terrestrial ; some have skin of body extended 

 between limbs ; fur usually soft. For the 

 most part lively and agile. 



2. Family. — Jerboas (Jerboidae). Head large ; eyes 



very prominent ; fore feet short, with five 

 toes ; hind legs and feet very long, with three, 

 four, or five toes ; tail very long and tufted ; 

 fur soft. Progress by leaps. 



3. Family. — Rats (Muridse). Teeth with tubercu- 



lar crowns; muzzle conical; nose somewhat 

 prolonged ; facial line nearly straight, or 

 slightly curved ; or with nose short and 

 blunt, and facial line more curved; ears 

 rounded ; tail long, tapering, and scaly, scan- 

 tily clothed with hair; toes usually long. 



4. Family. — Voles (Arvicolidse). Molars with flat 



crown ; head blunt ; facial lines much arched 

 body usually stout; tail scaly, sometimes 

 clothed, and rather tufted at apical portion, 

 generally about half the length of body, 

 sometimes longer. 



5. Family. — Mole-Rats (Spalacidse). Head large 



and blunt; eyes very small; sometimes fur 

 nished with cheek pouches; body thick, cy- 



