76 



GENUS SPERMOPHILUS. F Cuvier. 



DENTAL FORMULA. 



Incisive •= ; Canine j— r ; Molar j^ — 22. 



The dentition of the Spermophiles differs from that of the true mar- 

 mots, in the following particulars. The first longitudinal eminence (col- 

 line) is nearly obliterated, and the curve (talon) which unites the second 

 to the third, is prolonged much more internally, which makes the molars 

 of the Spermophiles more narrow transversely than longitudinally, as 

 compared ^vith those of the marmots. The teeth of the souslik (Spermo- 

 philus citilliis) were examined by F. Cuvier, and considered as typical of 

 this genus. 



Nose, convex ; ears, generally short ; cheek-pouches. 



Body, rather short ; mammae, pectoral and abdominal, from eight to 

 twelve. 



Feet, of moderate length, adapted for walking on the ground ; nails, 

 less in size than those of the marmots, less hooked than those of the 

 squirrels ; on the fore-feet, four toes, with the rudiment of a thumb, pro- 

 tected by a blunt nail ; second toe from the thumb longest, as in the 

 marmots, and not the third, as in the squirrels ; hind-feet, with five toes. 



Tail, generally rather short, and always shorter than the body ; in 

 several of the species, capable of a slightly distichous arrangement. 



The species belonging to this genus differ from the true marmots, not 

 only in their teeth, as shown above, but also in several other striking 

 particulars. They have cheek-pouches, of which the marmots are desti- 

 tute. They are by no means clumsy, and in form are rather slender, and 

 possess a degree of lightness and agility, approaching the activity of the 

 squirrels. 



With the genus Tamias, they assimilate so closely, that some of the 

 species present intermediate characters, and authors may well differ as 

 to which genus they ought to be referred to. Thus Tamias quadrivitta- 

 tus, and Spermophilus lateralis, seem to form a connecting link between 

 these two genera. It is to be recollected, however, that analogous cases 

 exist, not only among the mammalia, but in every class of animals, and 

 more especially in birds. 



