LAGOMYIDAZ 491 



one ha vinn some twelve transverse laminae. Upper incisors grooved. 

 Vertebrae: C 7, D 14, L 6, S 3, C 8. 



The Capybara (H. capyhara) is the largest existing Rodent, and the 

 only living representative of the genus. It is a bulky and stoutly 

 built animal, and attains a length of about 4 feet. The body is 

 covered with long and coarse hair, reddish-brown above and brownish- 

 yellow beneath. Capybaras are found over the whole of the 

 eastern part of South America, and to the westward range into 

 Bolivia and Peru. They frequent the borders of rivers and lakes, 

 concealing themselves among reeds and other water plants. Remains 

 of Hydrochcerus are found in the cavern-deposits of Brazil, which are 

 probably referable to the existing species ; one extinct species from 

 the Pleistocene of Buenos Ayres is estimated to have attained a 

 length of 5 feet, while H. magmis of the same deposits was of still 

 larger dimensions. The genus is also represented in the Pleistocene 

 of South Carolina and the infra-Pampean beds of Parana. 



Extinct Genera. — A number of South American fossil Rodents 

 have been referred to extinct genera of Caviidce. Thus Plexoclmrus, 

 from the Tertiary of Argentina, differs from Hydrochcerus in having only 

 nine lamina? in the last upper molar ; Cardiomys, Cardiatherium, etc., 

 from the infra-Pampeans are also stated to be allied to Hydrochoerus, 

 while Contracavia, of the same deposits, is related to Cavia, but of 

 larger size. Microcavia, again, from the Pleistocene of Argentina, is 

 regarded as connecting Cavia with Dolichotis. The Tertiary European 

 genera Issiodoromys and Nesocerodon are apparently referable to the 

 present family. 



Suborder Duplicidentata. 



Two pairs of incisors in the upper jaw (the second very small, 

 and placed directly behind the large first pair), the enamel of which 

 extends round to their posterior surfaces. At birth there are 

 three pairs of these incisors, but the outer one on each side is soon 

 lost. Incisive foramina large and usually confluent ; bony palate 

 ver}' narrow from before backwards ; no true alisphenoid canal ; 

 fibula ankylosed to the tibia, and articulating with the calcaneum. 

 Testes permanently external. This suborder includes the Picas, 

 Hares, and Rabbits, all of which are strictly terrestrial. 



Family Lagomyid^:. 



Complete clavicles, subequal limbs, no external tail, and short 

 ears. Skull depressed, frontals contracted and -without postorbital 

 processes ; ^i-orf; molars rootless, with transverse enamel-folds. 

 Palsearctic and Xearctic. 



Lagomys. 1 — Represented by about a dozen species of small 

 1 Cuvier, Tall, tl&mmb. dc VHist. Nat. p. 132 (1798). 



