COMPENDIUM OF GENERIC DISTINCTIONS. 



651 



Genus. — Lepus. 



Teeth.-I. ^, P. t* M. ?=? = 28. 



1—1 2—2 3—3 



Head. — Ears long. 



Limbs. — Hind-legs longer than fore-limbs. 



Tail. — Short, and curved upward. 



Habitat. — Europe, Asia, Africa, and America. 



Family. — Jerboid.e. 



Limbs. — Fore-feet Bhort. Hind-feet long, and formed for 

 leaping. 

 Tail. — Long, and thickly haired. 



Bub-family. — CMnchillina. 



Teeth.— Incisors smooth. Molars rootless, and composed of 

 narrow laminae. 



Genus. — Chinchilla. 



4 4 



Teeth. — M. , three laminae in each. 



4--1 



Head. — Ears large, rounded, and scantily haired ; whisker hairs 



very long. 



Limbs. — Fore-feet with five toes, hind with four. 



Habitat. — Peru. 



Genus. — Lagotis. 



Head. — Ears long, like those of the hare. 

 Limbs. — Fore-feet with four toes. 

 Habitat.— Peru. 



Sub-family. — Dipina. 



Teeth. — Molars with roots, and complex. 



Genus. — Helamys. 



1 -i i -i q o 



Teeth. — I. , P. , M. = 20. Incisors smooth and 



1-1 1—1 3-3 



broad. Molars with crown, divided into two portions by a fold 



of enamel. 



Head.— Ears long. 



Limbs. — Fore-feet with five toes, sharp, long claws ; hinder 

 with four toes, much elongated. 



Habitat. — South Africa. 



Teeth.— I. 



Genus. — Dipus. 



k* P. kd, M . *=* Z 16. 



1—1 1—1 2—2 



Upper incisors 



grooved, all slender and sharp. Molars with roots. 

 Head. — Ears short. 



Limbs. — Fore-feet with five toes, hind-feet with three. 

 Tail. — Long, covered with hair set in double row. 

 Habitat. — Part of Europe and Egypt. 



4—4 



with 



Sub-family. — Myox&na. 



Teeth. — Incisors smooth and compressed. Molars 



<± — t 

 roots, and with transverse bands on the crown. 



Genus. — Myoxus. 



Head. — Ears moderate, rounded, and covered with short, fine 

 hair. Whisker hairs, long. 

 Limbs. — Fore-feet with four toes, and a wart for thumb, without 

 ' claw. Hind-feet with five toes. 

 Tail. — Long and thickly haired. 

 Habitat. — Europe. 



Sub-family. — Sciurina. 



Teeth. — Incisors smooth, brown or orange-colored in front. 

 5—5 



Molars complex. M. 



4—4 



Limbs. — Forefeet with four toes, and clawed wart for thumb. 



Genus. — Sciuropterus. 



1 i o 2 3 3 



Teeth.— I. , P. — -, M. =22. Molars with tubercles. 



1—1 1—1 3—3 



Tail. — Rather short and flat. 



Development of skin along sides so as to form a flying mem- 

 brane. 

 Habitat. — India, North America, and Siberia. 



Genus. — Sciurus. 



Skin. — Not expanded along the sides. 



Head. — Cheek-pouches none. 



Habitat. —Europe, Asia, Africa, and America. 



Genus. — Tamias. 



Head. — Cheek-pouches. 



Feet. — Shorter than those of the true squirrels. 



Tail.— Shorter than the body. 



Habitat. — North America. 



Teeth.— I. 



Arctomys. 



4—1 



22. Incisors smooth and 



Genus.- 



=1, P. 1 =1, M. - 

 1—1 1—1 3—3 



rounded. Molars with tubercles set transversely on the crown. 



Head. — Cheek-pouches none. 



Limbs. — Fore-feet with four toes, and nailed wart for thumb ; 

 hind-feet with five toes. 



Tail. — Short, covered with long hair. 



Habitat. — Northern Europe and America. 



Genus. — Spermophilus. 



Head. — Cheek- pouches. 



Tail.— Moderate. General form more slender than Arctomys. 



Habitat. — Northern Europe and America, 



Teeth. 



4 4 



Molars - 



Family. — Aspalacid^e. 



Incisors very long, and visible outside the mouth. 



3-3 



3—3' 



Head. — Ears none, or very small. 

 Limbs.— Front, five toes, cloven. 

 General form, thick, heavy, and clumsy. 



Genus. — Spalax. 



O Q 



Teeth. — Molars , complex, and small. 



3—3 



Head. — Very flat, and abrupt at muzzle. 



the skin. Ears, none externally. 



Limbs. — Feet short, with small claws. 



Tail.— None. 



Habitat. — E u rope. 



Genus. — Batbyergus. 



Eyes hidden under 



Teeth.— I. 



= 20. Upper incisors with 



i, p. *=* m. 3 -=? 



1—1 1—1 3—3 



deep groove, a stripe of enamel across the crown. 



Head. — Eyes very small. Ears none externally. 



Limbs. — Large digging claws on fore-feet, the claw of second 

 toe the largest. 



Habitat. — Cape of Good Hope. 



Genus. — Saccophorus. 



4 4 



Teeth.— Incisors with deep longitudinal groove — Molars , 



rootless. 



Head. — Ears very small, and rounded. Eyes very small. Very 

 large cheek-pouches, nearly retractile when empty. 



Limbs.— Three middle claws of fore-feet long, the third the 

 longest. 



Tail.— None. 



Habitat. —Canada. 



N.B. Diplostoma may be separated from Saccophorus by the 

 smooth incisor teeth. 



