668 CLASS XVII. 



Body haiiy. Tail short or none. Ears rounded or oval, 

 moderate. 



These rodents, which have much affinity with Hystrix, were by 

 LiNNJEUS refen-ed to the genus Mus, by Klein, Pallas, Gmelin 

 united in a distinct genus, Cavia. They all live in South America. 



Cavia Cuv., Illig. (Spec, of the genus Cavia Pall., Gm.). 

 Incisors smooth anteriorly, white or pale yellow ; molars destitute 

 of roots, lamellose, in rows converging anteriorly, formed of two 

 triangular parts with cement filling the fissure between them. Feet 

 cloven, anterior tetradactylous, posterior tridactylous. (Dental for- 

 mula Owen, i. - — 7 , p. = , m. ^ — - — 20.) 



1 — 1 1 — 1 — 



Dolichotis Wagn. Ears broad at the base, somewhat large, more 

 than half the length of head. Feet high. Tail very short. 



Sp. Cavia patagonica Penn., Shaw, Mara magellanica Lesson Centurie 

 Zool. PI. 42, Waterh. Mamm. Ii. PI. 3, fig. i, Lievre pampa D'Azara; 

 this species has some resemblance to a hare, but differs (especially in the 

 high legs) from the other sjaecies of this genus, which it surpasses in size, 

 more in external aspect than in essential characters. 



Cavia (in the stricter sense). Ears rounded, much shorter than 

 half the head. Eeet short. Tail none. 



Sp. Cavia rupestrls Maxim. Ahh. zur NaturgescJi. Brasil. Lief. iv. Tab. 3; 

 Moco of the Brasilians. The sub-genus Kerodon of F. Cuv. Dents des 

 Mammif. PI. 48 ; greyish, below pale-coloured ; the hind legs ruddy ; lives 

 in the higher rocky regions of Brasil; — Cavia aperea Erxl., Maxim. 1. 1., 

 GuER. Iconogr., Mammif. PI. 32, fig. r, Sohreb. Sdugth. Tab. 173 a, fig. 

 3 ; with hair brown, at the point reddish-yellow ; throat pale ; lives in 

 grassy districts, at the edges of woods, throughout the greater part of 

 South America. It has been supposed that Cavia cohaya Schreb., Desm., 

 Mus porcellus L. (the guinea-pig, le Cochon d'Inde, das Meerschioeinchen), 

 BoFF. VIII. PI. I, Schreb. Sdugth. Tab. 173, is derived from this species. 

 This little animal, black with white and orange-coloured spots, procreates 

 very readily in Europe, and has often been submitted to physiological 

 experiments. See, respecting it, J. J. Nauman in Linn. Amoen. Acad. 

 IV. pp. 190 — 209; J. J. Ereuler Monographia Cavice Porcelli zoologica, 

 Gottingse, 1820, 4to. 



HydrocJioerus Briss. (not BoDD.), Illig., Cuv. Upper incisor 

 teeth indented anteriorly by a superficial longitudinal groove. Molar 

 teeth destitute of roots, lamellose, the posterior tooth of both jaws 

 large, composed of many lamellas. Head thick, protracted in front 



