FAMILY. 



HYSTEICIDAE. 



Molar teeth, = ; muffle, or terminal portion of the muzzle, clothed with pmall hairs ; the skull with a large ante- 

 orbital opening through which a portion of the masseter muscle passes as well as the infra-orbital nerve. Lower jaw with 

 the angular portion joined to the outer (not the under) surface of the bony covering of the inferior incisors. Tibia and 

 fibula distinct. 1 



The family of Hystricidae, of which the porcupine is a well known example, is almost entirely 

 American, and in fact chiefly confined to the southern portion of the continent, where most of 

 the species of Eodents belong to it. The only Old World species belong to the genera Hystrix, 

 Aulacodus, and Petromys. North America possesses but one genus, Erethizon, but Mexico, in 

 addition, has Cercoldbes, and perhaps some of the South American types may be found on its 

 southern borders. A few species occur in the West Indies, of which Capromys fournieri is the 

 most remarkable. 



The family Hystricidae , embracing as it does so great a variety of different forms, cannot be 

 so sharply defined as that of Leporidae with its two genera. Yery great diversity of opinion 

 has in fact existed as to the arrangement of the genera, many of which have been widely sepa 

 rated from their allies in a natural system of classification. By uniting those having the 

 features given at the head of the article, it will be found that the forms most closely allied in 

 reality are brought together, and an equal degree of harmony is established in the geographical 

 distribution of the species. 



The Hystricidae, as arranged by Waterhouse, are divisible into six sub-families, viz : Hystri- 

 cinae, Dasyproctinae, Echimyinae, Octodontinae, Chinchillinae, and Caviinae ; of these, only one, 

 viz., Hystricinae, is represented in the United States by species of Erethizon, erroneously referred 

 by most American authors to Hystrix, a genius of a different division of the sub-family. Mexico, 

 however, has an additional genus, Cercolabes, belonging to the same division. 



The chief characteristics of the six sub-families of Hystricidae, according to Waterhouse, are 

 as follows : 



I. CAVIIXAE. Molars rootless, divided by folds of enamel so as to form lobes having acute angles ; the series of molars 

 on opposite sides of the upper jaw converging and nearly meeting in front ; incisor teeth comparatively short, those of 

 the lower jaw not being extended backwards as far as the springing of the angular portion or descending ramus. Four 

 toes to the fore feet, and three to the hind. Tail wanting, or rudimentary. Upper lip entire. A strongly developed hori 

 zontal ridge on the outer surface of the lower jaw ; the angular portion of this jaw produced much beyond the condyloid 

 portion, descending below the level of the dentary portion, and with a curved lower margin. Clavicles wanting. 



The principal genera of this family are Dolicliotis, Cavia, and Hydroclwerus, the latter, in 

 cluding the Capybara, or Capinche, the largest of living Rodents. 



II. CIUNCHILLINAE. Molars rootless, with parallel or nearly parallel transverse plates of enamel ; the series of molars on 

 either side of each jaw converging in front. Tail long, or of moderate length, recurved and bushy. Clavicles perfect, 

 slender. Fibula very slender. Hind feet with less than five toes. 



1 Waterhouse. Nat. Hist. Mamm. II, 1848, 147. 



