678 CLASS XVIT. 



Neotoma SAY and ORD. Incisors smooth, yellow in front; 



Q _ g 



mo l ars _ _ y complex. Ears exsert, somewhat large, oval. Feet 

 pentadactylous. Tail long, clothed with long hair. 



Sp. Neotoma Drummondii, RICHARDSON Fauna lor. Amer., Mainm. p. 137, 

 PI. vn. (vni.), North America ; the habitus resembles that of Myoxus or 

 Chinchilla, more than that of Mus; Neotoma floridanum SAY. 



Sigmodon SAY and ORD. 



Sp. Sigmodon hispidum SAY and ORD, Arvicola hortensis HARLAN Faun. Am. 

 (a species unknown to me). 



Hypudceus ILLIG. (in part), Arvicola LAC., Cuv. Incisor teeth 



/3 _ 3\ 

 smooth, molars fa s) complex, with folds of enamel describing 



triangles, alternating in a double row on the surface of the crown. 

 Ears moderate or small, rounded, almost concealed under the hair 

 of head. Fore feet tetradactylous with hallucar wart, hinder pen- 



tadactylous; claws small; soles naked. Tail moderate or some- 



i _ i -^ _ -^ 2 _ 2 

 what short, hairy. Dent. form. OWEN, i. y - , p. , m. 



16. 



Sp. Hypudceus amphibius ILLIG., Mus terrestris et amphibius L., BUFF. vn. 

 PI. 43, SCHREB. Saugth. Tab. 186, Cuv. R. Ani., 6d. ill., Mamm. PI. 58, 

 fig. 3; the water-rat, le rat d'eau; 7" long besides the tail, which is 3" or 

 more long ; brownish, grey below ; as varieties of this species are regarded 

 Mus terrestris (L?) HERMANN, which is smaller, Arvicola destructor SAVI 

 and. Arvicola monticola DE SELYS-LONGCH. Hypudceus arvalis, Musarvalis 

 PALL., BUFF. vn. PI. 47, SCHREB. Saugth. Tab. 191; the field- campagnol, 

 meadow-mouse, of the size of a mouse ; tail only one-third the length of 

 the body ; colour yellowish-grey, below whitish-grey. This species is, like 

 Mus sylvaticus, very numerous in some years, so as almost to destroy the 

 harvest ; such was the case in 1 8 1 8 and 1819 in Holland and elsewhere ; 

 see C. NICATI Commentatio de Mure domestico, sylvatico atque arvali in 

 Annal. Acad. Kheno-Traject. 1823. 



Hypudceus ceconomus ILLIG., Mus ceconomus PALL., SCHREB. Saugth. 

 Tab. 190; GUERIN Iconogr., Mammif. PI. 26, fig. 3; this species, at home 

 in Siberia, lays up a great quantity of roots, &c. against winter, and 

 travels away at indeterminate times in numerous troops. 



Compare on this genus DE SELYS-LONGCHAMPS Etudes de Micromam- 

 malogie, 1839, pp. 81 132; the same in Revue zoolog. 1847, pp. 305 312, 

 and GERBE Revue et Magas. de Zool. 1852, pp. 257 270, 305 312, 

 44946o, PL ii, 13, 14, 1 8, 19. 



