MAMMALIA. 469 



usual, on vegetable substances. One species only is described, and belongs 

 to the northwest portion of North America, the sewellel of Lewis and Clark 

 {Ä. leporina). A second species is indicated, if the characters alluded 

 to bv the author are not differences occurring in the young. 



The genus Arctomys (the marmots) has, like the squirrels, five molars 

 above and four below, all of them bristled with points ; accordingly some 

 species are inclined to eat flesh and feed upon insects as well as grass. As 

 to their general form, the marmots are the very reverse of the squirrels, 

 being heavy, provided with short legs, a middle-sized or short hairy tail, 

 and a large, flat head, passing the winter in a state of torpor and shut up in 

 deep holes, the entrance of which they close with a heap of grass. They 

 live in societies, and are easily tamed. The alpine marmot, A. marmotta or 

 alpinus {pi. 113, fig. 11), is about the size of the hare. Four species are 

 described from North America, among which is the common Maryland mar- 

 mot, or ground-hog {A. monax) of the northern, eastern, and middle states. 



The genus Spermophilus possesses cheek pouches, two incisors above 

 and below, and five molars above and four below, exactly as in the ground 

 squirrels ; but whilst the external appearance of the latter is more like 

 that of squirrel proper {Sciuriis), the general appearance of Spermophilus 

 is more that of the marmots, from which it is distinguished by the dentition. 

 The molars are more narrow transversely than longitudinally. The ears 

 are generally short. The feet are of moderate length, adapted for walking 

 on the ground ; the nails are inferior in size to those of the marmots, and 

 less hooked than those of the squirrels. There are four toes to the fore 

 feet, with the rudiment of a thumb protected by a blunt nail ; the hind feet 

 have five toes. The tail is always shorter than the body. The form of the 

 body is rather slender, and possesses a degree of lightness and agility 

 approaching the activity of the squirrels. Twelve species of this genus 

 are known to exist in North America, three in Europe, and a few in 

 Asia and Africa, if some of the latter are not to be referred to the genus 

 Arctomys. 



In North America they are commonly known by the names of marmot 

 squirrels, prairie marmot or prairie dog, tawny American marmot, leopard 

 marmot, small grey squirrel (Lewis and Clark), and other similar appella- 

 tions more or less arbitrary. They chiefly inhabit the northern regions. 

 The following is an extract from Say, in Long's Expedition to the Eocky 

 Mountains, on the habits of the prairie dog {S. ludovicianus): 



" This interesting and sprightly little animal has received the name of 

 prairie dog, from a fancied resemblance of its warning cry to the hurried 

 barking of a small dog. The sound may be imitated by the pronunciation 

 of the syllable ' chek, chek, chek ! ' in a sibillated manner, and in rapid 

 succession, by propelling the breath between the tip of the tongue and the 

 roof of the mouth. As particular places are in general occupied by the 

 burrows of these animals, such assemblages of dwellings are denominated 

 p)ra{rie dog villages by the hunters. They vary widely in extent, some 

 being confined to an area of a few miles, others bounded by a circum- 

 ference of many miles. Only one of these villages occurred between the 



ICONOGRAPHIC ENCYCLOPEDIA. — VOL. II. 43 673 



