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VERTEBRATA. 
THE HYSTEIOID^. 
THs family embraces a mimBer- of tribes,, all bearing more or less resemblance to the well-incwn 
Porcupine^ whose scientific name is Hystrix^ and thus furnishes the title of the group. Most of 
these have some resemblance to the hog, from the nature of their hair, the form of their body, 
and their manner of walking, as well as in some less important particulars. Their size, though 
less than that of tlie hog, is still superior to most other rodents. They all have four pair of molar 
teeth, the crowns of which exhibit sinuosities more or less, complicated. The cranium and jaws 
also present some peculiarities. The tribes included in this family we shall notice under the 
names of Caviens, Gelogemjens^ Dasyproctiens^ Hystriciens^ Aulacodicns, Mrethizoniens^ Chinchil- 
liens or Callomyens, and Anomalicriens^ 
THE CAYIENS OR CAVIINA. 
This tribe has the following characteristics : molar teeth 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 backward 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 horizontal 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 dental portion, and with a curved lower margin; clavicles wanting. 
