HYSTRICOMORPHA. 359 
Secrion III.—HYSTRICOMORPHA. 
PORCUPINE-LIKE RODENTS. 
This section contains six families, viz. :— 
Octodontide .. = 3 sub-families, 18 genera. 
Alystricide = 2 sub-families, 5 genera. 
Chinchillide .. = 5 genera, of which two are fossil. 
Dasyproctida .. = 2 penera 
Dionymide = I genus. 
Cavide + .« = 3 genera. 
Of these we have to deal with but one, the second family, Hystricide, 
the rest belonging to Africa in part, but the majority to the American 
continent, chiefly South America. 
I give the general characteristics of the section as laid down by 
Mr. Alston :— 
“One premolar above and below (except in Crenxodactylus) ; grinding 
‘teeth rooted or rootless, not tuberculate ; frontals with no distinct post- 
orbital processes (except in Cefomys); infra-orbital opening large, 
subtriangular, or oval ; zygomatic arch proportionately stout ; molar not 
advancing far forward, (except in Ctenodactyline and Chinchillide) and 
not supported below by a continuation of the maxillary zygomatic 
process ; incisive foramina small; foramina in the base of skull propor- 
tionally large; an inter-pterygoid fissure; mandible with its angular 
portion springing from the owéer side of the bony covering of the lower 
incisor, triangular, usually pointed behind ; coronoid process small, and 
condyle low ; clavicles perfect or imperfect ; fibula persistent as a distinct 
bone throughout life ; upper lip rarely cleft ; muffle clad with fine hairs ; 
nostrils pointed above, sigmoid or linear; ears usually emarginate be- 
hind ; tail hairy, sub-naked, or scaly.” —‘ P. Z. S.,’ 1876, p. go. 
As I have said before, we have only to do with the AMystricide or 
Porcupines, but many of the others are familiar by name. Of the 
Octodontide the best known is the coypu of the Andes, one of the 
largest of the rodents, and the ground-rat or ground-pig of western and 
southern Africa. The chinchilla, which is the typical form of the 
third family, is known to all, especially ladies, from its delicate soft fur. 
The agouti of South America is the representative of the Dasyproctide. 
The family Dinomyide consists of one animal only, Dinomys Branickit ; 
the only known example of which was obtained in Peru on the Montana 
de Vitoc. It was’ found walking about in a yard at daybreak, and 
showed so little fear of man that it suffered itself to be killed by the 
stroke of a sword. It is a pity no one was sensible enough to try and 
