"One premolar above and below (except in Ctenodactylus); grinding teeth rooted or rootless, not tuberculate; frontals with no distinct post-orbital processes (except in Chætomys); infra-orbital opening large, sub-triangular, or oval; zygomatic arch proportionately stout; molar not advancing far forward, (except in Ctenodactylinæ and Chinchillidæ) and not supported below by a continuation of the maxillary zygomatic process; incisive foramina small; foramina in the base of skull proportionally large; an inter-pterygoid fissure; mandible with its angular portion springing from the outer 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 behind; tail hairy, sub-naked, or scaly."—'P. Z. S.,' 1876, p. 90.
As I have said before, we have only to do with the Hystricidæ or Porcupines, but many of the others are familiar by name. Of the Octodontidæ 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 Dasyproctidæ. The family Dinomyidæ consists of one animal only, Dinomys Branickii; 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 take it alive. As yet nothing is known of its habits. Of the last family, Caviidæ, the cavy and the capybara are well known to travellers in South America, and the common guinea pig is familiar to us all.
[FAMILY HYSTRICIDÆ—THE PORCUPINES.]
| Skull of Porcupine. |
In this family the hairs of the body are more or less converted into spines or quills; the form of the skull is peculiar, being ovate, often greatly inflated with air cavities in the bones; the facial portion is broad and short; the malar portion of the zygomatic arch has no inferior angular process as in the Octodontidæ; the occipital plane or hinder-surface is perpendicular, with a median ridge; the incisor teeth are large and powerful; the molars with external and internal folds, four in each jaw. The form is robust; limbs sub-equal; fore-feet with four toes, and a small wart-like thumb; hind-feet with four and five toes; tail long in some, short in others. There are two sub-families—Sphingurinæ and Hystricinæ. With the genera of the first we have nothing to do. They include the prehensile-tailed porcupines of South America, Sphingurus prehensilis, S. villosus, and S. Mexicanus, all arboreal forms, and the Canada porcupine (Erythizon dorsatus) which is covered with woolly hairs and spines intermixed. The true porcupines, sub-family Hystricinæ, consist of two genera, both of which are represented in India—Atherura and Hystrix.
[SUB-FAMILY HYSTRICINÆ—THE TRUE PORCUPINES.]
Grinding teeth semi-rooted; skull rather more elongate; infra-orbital foramen of great size; clavicles imperfect, attached to the sternum, and not to the scapula; upper lip furrowed; tail not prehensile; soles of feet smooth. The female has six mammæ. In these points they differ from the American arboreal porcupines (Sphingurus), the skull of which is very short, the tail prehensile, the soles of the feet tuberculated, and the female has only four mammæ.
The two genera, Atherura and Hystrix, which compose this sub-family, are distinguished by long tail and flattened spines (Atherura); and short tail and round spines (Hystrix).