SECTION III.--PORCUPINE-LIKE RODENTS (_HYSTRICOMORPHA_). FAMILY XI.--OCTODONTIDÆ. This first family of the Porcupine alliance consists of a number of rat-like animals, nearly all of which are inhabitants of South America, three species only being peculiar to the large West Indian Islands, whilst, singularly enough, four more are known from different parts of the African continent. Except in one of these last, all the members of the family have four molars on each side in each jaw, and the crowns of these teeth show internal and external folds of enamel. The malar portion of the zygomatic arch has an angular process at its lower margin. The hind limbs are not disproportionately developed, and both they and the fore feet are nearly always furnished with five toes, armed with curved claws; and the clavicles are perfect. The ears are generally short and sparingly hairy, and the tail, which is of various lengths, is either clad with short hairs, or naked and scaly. We may begin with two African species of this generally American family, which have the two inner claws of the hind feet furnished with comb-like fringes of horny bristles, whence the name of _Ctenodactylus_ has been applied to the best known species. These two species, which exhibit strong affinities to the Jerboas, form the sub-family CTENODACTYLINÆ. The GUNDI (_Ctenodactylus Massoni_) has only three molars on each side in each jaw, and only four toes upon each foot. It is an animal about the size of the Water Rat, but with a mere stump of a tail, very small ears, very long whiskers, and the hind limbs rather longer than their fellows. It lives in North Africa, chiefly on the borders of the Sahara, where it takes up its abode in the rocky hills, and descends therefrom to the cultivated grounds to feast upon the growing corn. It is diurnal in its habits, but exceedingly shy and watchful, making off to its fastnesses at the least appearance of danger. _Pectinator Spekei_, a species named after its discoverer, the celebrated African traveller, is nearly related to the preceding, but has a small additional molar in each series. The tail is of moderate length, and bushy, and the ears have a small antitragus. It inhabits the Somali land in the interior of North-eastern Africa. [Illustration: DEGU.]