490 RODENTIA 
distributed throughout South America, extending even to the Straits 
of Magellan. The Restless Cavy (C. porcellus), which is found 
throughout Uruguay and Brazil, has been very generally regarded 
as the ancestral form of the domesticated Guinea-Pig. It is about 
10 inches long, and weighs a little over a pound; its fur is long 
and of a nearly uniform grayish-brown colour. This species is 
rarely found in dry sandy localities, preferring marshes covered 
with aquatic plants, among which it lies concealed, feeding in the 
early morning and after sunset in the evening; but when the soil 
is dry it forms burrows. It lives in societies of from six to eighteen 
individuals, breeding but once a year, with one, or at most only two, 
young at a birth. The Guinea-Pig (probably a misnomer of Guiana- 
Pig) is larger than C. porcellus, and is regarded by Dr. Nehring as 
descended from another species, C. cuéleri. It is white in colour, 
with irregular patches of reddish-brown and black. The Bolivian 
Cavy (C. boliviensis), found throughout the higher regions of Bolivia, 
usually at an elevation of 10,000 or 12,000 feet, is exceedingly 
shy, and lives in burrows, which in some districts are so numerous 
as to have completely undermined the soil. The Rock-Cavy 
(C. rupestris), distinguished by its short, blunt nails, is found in rocky 
situations throughout Brazil, and is much sought after for its flesh. 
The Southern Cavy (C. australis), common along the coast of Pata- 
gonia, forms deep burrows, with several outlets, in sandy declivities. 
Remains of existing species of Cavia are found in the cavern- 
deposits of Lagoa Santa, Brazil. 
Dolichotis.A—Characterised by the great length of the ears and 
the short tail. The palate is so much contracted in front that the 
premolars of opposite sides touch by their antero-internal edges. 
Vertebre: C7, D12, L8, 8 3, C10. 
The Patagonian Cavy (D. patuchonica)—the only living repre- 
sentative of the genus—is rather larger than a Hare, which it 
somewhat resembles in external appearance. It inhabits the dry 
sterile districts of Patagonia and La Plata, disappearing wherever 
the country becomes more humid. This animal burrows in the 
earth, although in districts where the Viscacha is found it is said 
to avail itself of the works of the latter. Unlike other cavies, its 
eyes are protected from the glare of the sun by prominent eyelashes. 
The body is covered with a long dense fur of a rusty colour. Two 
young are produced at a birth. Three species of Dolichotis have 
been described from the Brazilian cave-deposits, one of which is 
probably not really separable from the existing form. 
Hydrocherus.-—A. large aquatic form with all the feet fully 
webbed ; the skull (Fig. 213, p. 481) large, with enormous par- 
occipital processes ; and the molars very complex, the third upper 
1 Desmarest, Mammalogie, p. 360 (1822). 
° Erxleben, Syst. Reg. Animal, p. 191 (1777) ; ex Brisson. 
