88 MAMMALIA. 



of vision, since the skin passes over it without opening or even growing thinner, 

 and being as much covered with hair as any other part. It is rather larger 

 than our rat; its fur is smooth, and of an ash -colour, bordering on a red. 

 This is the animal, in the opinion of Olivier, to which the ancients alluded when 

 they spoke of the mole as being perfectly blind. 



From the Rat-Moles themselves should have been separated the 



BATHYERGUS, Illiger, ORYCTKRES, Fr. Cuvier, 



Which, with the general form, feet, and truncated incisors of that genus, have 

 four grinders throughout. Their eye, though small, is visible, and they have a 

 short tail. 



B. maritimus. (The Maritime Rat- Mole.) Nearly the size of a rabbit; the 

 superior incisors furrowed with a groove, and the hair of a whitish grey. 



GEOMYS, Rafinesqne PSEUDOSTOMA, Say. 



Which have four compressed prismatic molars throughout, the first double, the 

 remaining three simple ; the upper incisors furrowed with a double groove in 

 front ; five toes to each foot ; the three middle anterior nails, that of the medius 

 particularly, very long, crooked, and trenchant They are low animals, and 

 have very deep cheek-pouches, which open externally, enlarging the sides of 

 the head and neck in a singular manner. One species only is known, 



G. bursarius. (The Canada Hamster.) Size of a rat ; fur of a reddish- 

 grey ; tail naked, and but half the length of the body. Inhabits deep burrows 

 in the interior of North America. 



DIPLOSTOMA, Rafinesque. 



The Diplostomse are almost precisely similar to the Geomys, but they have 

 no tail. These animals are also from North America. The species before us 

 is reddish, and ten inches in length. 



We now pass to larger Rodentia than those of which we have hitherto 

 spoken, but of which several still have well defined clavicles. Of this number 

 is the 



CASTOR, Linn tens. 



The Beavers are distinguished from all other Rodentia by their horizontally 

 flattened tail, which is nearly of an oval form, and covered with scales. They 

 have five toes to each foot: those of the hinder ones are connected by mem- 

 branes, and that next to the thumb has a double and oblique nail. Their 

 grinders, to the number of four throughout, and with flat crowns, appear as if 

 formed of a doubled bony fillet, or so as to show one sloping edge at the 

 internal extremities of the upper row, and three at the external; in the lower 

 ones it is exactly the reverse. 



Beavers are large animals, whose life is completely aquatic ; their feet and 

 tail aid them equally in swimming As their chief food is bark, and other hard 



