486 RODENTIA 
Chetomys.1—Distinguished by the shape of its skull and the 
greater complexity of its teeth. It contains only one species 
(C. subspinosus), a native of the hottest parts of Brazil. 
Subfamily Hystricinzee.—Molars semi-rooted; clavicles incom- 
plete; soles smooth ; a rudimentary pollex; six mamme ; tail not 
prehensile. Now confined to the Old World, where they occur in 
Southern Europe, Africa, India, and the Malay Archipelago as 
far eastwards as Borneo. Habits terrestrial and nocturnal. Three 
genera, 
Hystriz.2—This genus is readily characterised by the inflated 
skull, in which the nasal chamber is often considerably larger than 
Fig. 215.—The Common Porcupine (Hystrix cristata). 
the brain-case, and by the short tail, tipped with numerous slender 
stalked open quills, which make a loud rattling noise when the 
animal moves. Vertebre: C 7,D15,L4,8 4,012. The best- 
known member is the Common Porcupine (H. cristata, Fig. 215), 
which occurs throughout Southern Europe and North and West 
Africa, but is replaced in South Africa by H. africe-australis, and 
in India by the Hairy-nosed Porcupine (H. leucura). 
The following account of the habits of the last-named species 
is from Dr. Jerdon: “ Hystria leucwra is found over a great part of 
India, from the lower ranges of the Himalayas to the extreme south 
but does not occur in lower Bengal, where it is replaced by H. 
bengalensis. It forms extensive burrows, often in societies, in the 
sides of hills, banks of rivers and nullas, and very often in the 
1 Gray, Proc. Zool. Soc. 1843, p. 21. 
* Linn. Syst, Nat. 12th ed. vol. i. p. 76 (1766). 
