in the Collection of the British Museum. 271 



I. Without any cheek-pouches. Fur soft, consisting of fusiform 

 hairs and a soft under-fur. Ears ovate. Arboreal. Tree- 

 Squirrels. 



A. The limbs free, without any parachute. 



I. The front edge of the cutting-teeth broad, rounded, closely longi- 



tudinally grooved. 



1. Rheithrosciurus. Ears large, long, pencilled; head 

 large, short; tail broad, clavate. 



ir. The front edge of the cutting-teeth narrow, compressed, smooth. 



2. SciuRUS. Ears ovate, pencilled or tufted externally ; nose 

 rounded ; tail longer than the body. 



3. Macroxus. Eai's ovate, covered with short adpressed 

 hairs ; nose short, blunt ; cheek-pouch none ; tail longer than 

 the body. 



4. Rhinosciurus. Ears ovate, covered with short adpressed 

 hairs ; nose acute, produced ; cheek-pouch none ; tail longer 

 than the body. 



B. The limbs enclosed in skin, forming a jmrachute ; tail short, 

 broad, pennate ; front edge of cutting-teeth smooth. 



5. SciUROPTERUS. Ears ovate, covered with short adpressed 

 hairs. Europe, Asia, and America. 



II. Without any cheek-pouches. Fur short, rigid, with flat chan- 



nelled spines, without any under-fur. Ears rounded, scarcely 

 raised. Terrestrial. Ground-Squirrels. 



6. Xerus. Ears narrow, short, mostly raised above the head ; 

 face short, blunt; cheek-pouches none; fur short, rigid. Africa. 



III. With distinct cheek-pouches. Fur soft, consisting of fusiform 

 hairs arid a soft under-fur. Ears ovate. Fossorial. Bur- 

 rowing Squirrels. 



7. Tamias. Ears ovate, covered with short adpressed hairs ; 

 face short, rounded; cheek-pouches distinct. Europe, North 

 Asia, and America. 



I. Without any cheek-pouches. Fur soft, consisting oj fusiform 

 hairs and a soft under-fur. Ears ovate. Arboreal. Tree- 

 Squirrels. 



A. The limbs free, without any parachute. 



I. The front edge of the cutting-teeth broad, rounded, closely longi- 

 tudinally grooved. 



1. Rhetthrosciurus, nov. gen. 



Head lai'ge, compressed, short; ears large, with a pencil of 

 elongated hairs at the tip ; cutting-teeth broad, rounded in front 



