133 



nostrils are lateral, the whiskers sparse, but some of them nearly half as 

 long as the body. The cylindrical tail tapers uniformly to a fine point, 

 with a slight pencil of hairs at the tip ; it is covered with verticillate 

 scales, with short hairs springing from beneath the whorls, but not con- 

 cealing them. The eyes are small, situated midway between the nose 

 and ear. The ear is remarkable among rodents for the development of 

 the antitragus in the form of a circular, thickened pad, completely re- 

 versible, and capable of being f applied against the meatus; thie tragus 

 expands into a thin, free, rounded border, which may lie in apposition 

 with the opposite autitragal lobe, thus providing for the perfect closure 

 of the meatus. The hands are large, the thumb rudimentary, covered 

 with a broad, truncated nail; the third and fourth fingers longest. The 

 lengthening of the hind limbs, which determine the saltatorial habits 

 of this species, is effected by the elongation of both the eras and the pes ; 

 the former is longer than the latter. The toes are five, tbe second, third, 

 and fourth sub equal, and much the longest; all have claws. The meta- 

 tarsals are five, complete from end to end. (Coues.) The foot is covered 

 above with short, silky hairs, below naked; the sole is smooth about half 

 way, then grauular ; the digits are transversely scutellate below. The 

 general pelage is coarse and hispid, with but little gloss; bristly haiis 

 are mixed with the soft, under fur. The under parts are snowy white, 

 sharply separated from the sandy-yellowish of the sides and outer sur- 

 faces of the limbs. There is a dorsal strip of brownish-yellow, heavily 

 shaded with brownish-black ; this is about as wide as the lateral stripes 

 already described. The tail is bicolor, corresponding to the body-areas ; 

 the ears have a light colored rim; the backs of the hands and feet are 

 whitish ; the whiskers are mostly black. 



FAMILY MURIDJ5. 



The family Muridx includes Rodents, which have the incisor teeth j-\ > 

 canines and premolars .absent ; molars |:f ; equal sixteen teeth in all. 

 Tibia and fibula united below. The coronoid, condylar, and descending 

 processes of the mandible are well developed and distinct. The ante- 

 orbital foramen is a large pyriform slit, bounded exteriorly by a broad 

 plate of the maxillary; this character is probably diagnostic of the fam- 

 ily. The American genera are incluaed in two sub-families : 



Murinas. — Animals which include and resemble the oomiLoa Eats and 

 Mice. The molars are rooted, tubercular, and with crenate periphery. 

 Incisors compressed, narrower than deep.; root of outer incisor causing a 

 protuberance on outer side of mandible ; descending process of the man- 

 dible, a broad flattened plate, wholly below the plane of the molars ; pal- 



