352 JOURNAL, BOMBAY NATURAL HLST. SOCIETY, Vol. XXVI. 



Suborder I. — Simplicidextata. 



The Families of this Suborder may be arranged in a key as 

 follows ; — 



Key to the families of Simplicidentata. 



A. Angular portion of mandible arising 

 from lower edge of bony socket of 

 incisors. 



a. Fibula distinct ; skull with distinct 



postorbital processes ; premolars 

 two on each side in the upper jaw, 

 only one in the lower ... ... I. SciURiDiE. 



b. Fibula united to tibia ; no postorbital 



processes. 

 a\ Form slender ; tail long. 



a^ Premolars one on each side 



in upper jaw... ... ... II. DiPODiD^. 



Jf. Premolars absent. 



a. Tail clothed with long hair 

 which grows continually 

 longer towards the tip ... III. GliriDjE. 



h\ Tail clothed at most with 

 short hair, occasionally 

 forming a tassel at the 

 extreme tip ... ... IV. MuRiD^. 



6\ Form heavy, mole-like ; tail short 



or rudimentary. ... ... V. SPALAClDiE. 



B. Angular portion of mandible arising 



from outer side of bony socket 

 of incisor ; body more or less 

 covered with spines ... ... VI. HySTRiciDyE. 



Family I. — SciukiDjE. 



The two Subfamilies may be distinguished as follows : — 

 Key to the Subfamilies of Sciurid^. 



A. Form slender; tail long; incisors 



compressed; arboreal ... ... I. SciURi>'^. 



B. Form stout ; tail generally short ; 



incisors not compressed ; terrestrial. II. Marmotin^. 



