CLASS I. MAMMALIA: ORDER 7. RODENTIA, 



301 



\ x 







THE ROCK CAVY. 



of Bnffon; the Ferkd-ynaus of the Germans. It is sometimes called Coui-coui, from its cry. There 

 is both a wild and a domestic breed. In a wild state, it has the incisors white ; fur long, and 

 somewhat coarse, and on the upper parts of the sides and body distinctly penciled with black and 

 dirty yellow; chest gray-brown, throat and abdomen pale, dirty yellow, or sometimes brown-gray. 

 It is of the size of a large rat, its legs very short, its neck short, and its body very clumsy. It has 

 no tail. It inhabits the banks of the Rio de la Plata, and extends northward into Paraguay. 

 Bolivia, and Brazil. It is known by the name of Aperea, and it is exceedingly common in the 

 neighborhood of several towns on the banks of the Rio de la Plata, sometimes frequenting the 

 sand hillocks, or the hedge-rows formed of the Agave and Opuntia ; but marshy places, covered 

 with aquatic plants, appear to be preferred. 



Where the soil is dry, it makes a burrow, but otherwise lies concealed amid the herbage. It 

 generally comes out to feed in the evening, and if the day be gloomy, it will likewise make it: 

 appearance in the morning. Mr. Bridges states that this animal in Bolivia is confined to the low 

 lands, and in this respect differs from the Cavia Boliviensis, which is always found at a consider- 

 able elevation. It is not uncommon in fields in the neighborhood of Chuquisaca and Cochab- 

 amba, and takes shelter among the loose stones of the walls by which the fields are inclosed. In 

 Paraguay it generally frequents moist situations, and near the borders of forests, but it never 

 occurs either in the forests or in the open fields. It lives in little societies of from six to fifteen 

 individuals, in the impenetrable groves of bromelias, and its presence is detected by numerous 

 little beaten paths which it forms among these plants. It feeds early in the morning and' after 

 sunset in the evening, but never strays far from its home. It is stated that it breeds but once in 

 the year, and then has but one or two young. . . 



The Domestic Guinea-Pig, or Cobaya, or Axcema, the Mus jwrcellus of Linnaeus, is probably 



the descendant of the wild species just described, though this some naturalists doubt, as the 



, Aperea is said to breed but once a year, and to produce only one or two at a time, while the do- 



' mestic animal is prolific as a rabbit ; the color, also, of the tame variety is greatly diversified. In 



