COMPENDIUM OF GENERIC DISTINCTIONS. 



791 



Genus. Helamys. 



I i i i 33 



Teeth. I. , P. , M. , = 20. Inci- 



i i i i 33 



sors smooth and 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. 



Genus. Dipus. 



i i i i 22 

 Teeth. I. , P. , M. , = 16. Upper 



I I I I 2 2 



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. 



Sub-family. Myoxlna. 



Teeth. Incisors smooth and compressed. Molars 

 44 



, with roots, and with transverse bands on the 



44 

 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. 



H abitat . E u rope. 



Sub-family. Sciurtna. 



Teeth. Incisors smooth, brown or orange-col- 



55 

 ored in front. Molars complex. M. . 



44 



Limbs. Fore-feet with four toes, and clawed 

 wart for thumb. 



Genus. Sciuropterus. 



i i 22 33 



Teeth. I. , P. , M. = 22. Molars 



i i i i 33 



with tubercles. 



Tail. Rather short and flat. 



Development of skin along sides so as to form a 

 flying membrane. 



Habitat. India, North America, and Siberia. 



Genus. Sciurus. 



Skin. Not expanded along the side. 



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. 



Genus. Arotomys. 



i i I i 4 4 . 



Teeth. I. , P. , M. , = 22. Insci- 



i i i i 33 



sors smooth and 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 Arotomys. 



Habitat. Northern Europe and America. 



Family. As PALAciD.*. 

 Teeth. Incisors very long, and visible outside 



44 33 

 the mouth. Molars or . 



44 33 



Head. Ears none, or very small. 

 Limbs. Front, five toes, cloven. 

 General form, thick, heavy, and clumsy. 



Genus. Spalax. 



33 

 Teeth. Molars , complex, and small. 



33 



Head. Very flat, and abrupt at muzzle. Eyes 

 hidden under the skin. Ears, none externally. 

 Limbs. Feet short, with small claws. 

 Tail. None. 

 Habitat. Europe. 



Genus. Bathyergus. 

 33 



Teeth. I. 



I i i 



-, P. , 



M. 



20. Upper 



33 " 33 



incisors with deep groove, a stnpe 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. Sacc6phorus. 

 Teeth. Incisors with deep longitudinal groove 



44 

 Molars , rootless. 



44 



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 Sacc<S 

 phorus by the smooth incisor teeth. 



Genus. Rhi'zomys. 

 Teeth. incisors broad, smooth, and red in front ; 



i 3 ~ 3 

 molars . 



3 3 

 Head. Broad, short, and abruptly terminated in 



front. Ears very small. Eyes also small. 



Limbs. Fore -feet four-toed, with clawed wart 

 for thumb. 



Habitat. Malacca and China. 



