In the New World the porcupines are represented by the members of the family Erethizontidae, or Coendidae, which have rooted molars, complete collar-bones.
The policy of the government which protects game, both in the park and in the surrounding national forests, has induced elk, deer, antelope, mountain-sheep, bears, porcupines, coyotes, squirrels, gophers and woodchucks to take shelter here.
In most species there are three circumvallate papillae at the base, and the apical portion is generally covered with small, thread-like papillae, some of which in the porcupines become greatly enlarged, forming toothed spines.
The scapula is usually narrow, with a long acromion; the clavicles may be altogether absent or imperfect, as in porcupines, cavies and hares, but in most species are well developed.
As the drum revolves at a good speed, the silk is drawn by the steel teeth through the porcupines into the drum in more or less straight and parallel fibres.
In the order of Rodents squirrels are very numerous, and porcupines of two genera are met with.
The wild animals found in the district comprise a few tigers, leopards and wild elephants, deer, wild pig, porcupines, jackals, foxes, hares, otters, &c. The green monkey is very common; porpoises abound in the large rivers.
Synetheres, or Coendu, contains some eight or ten species, known as tree-porcupines, found throughout tropical South America, with one extending into Mexico.
They are of a lighter build than the ground-porcupines, with short, close, many-coloured spines, often mixed with hairs, and prehensile tails.
All rodents, with the sole exception of the dormice, have a caecum, often of great length and sacculated,, as in hares, the water-rat and porcupines; and the long colon in some, as the hamster and water-rat, is spirally twisted upon itself near the commencement.
In the squirrels and porcupines the tibia and fibula are distinct, but in rats and hares they are united, often high up. The hind foot is more variable than the front one, the digits varying in number from five, as in squirrels and rats, to four, as in hares, or even three, as in the capybara, viscacha and agouti.
The fur varies exceedingly in character, - in some, like the chinchillas and hares, being fine and soft, while in others it is more or less replaced by spines on the upper surface, as in spiny rats and porcupines; these spines in several genera, as Xerus, Acomys, Platacanthomys, Echinothrix, Loncheres and Echinomys, being flattened.
In porcupines and hares the tendons of the flexor digitorum longus and flexor hallucis longus are connected in the foot, while in the rats and squirrels they are separate, and the flexor digitorum longus is generally inserted into the metatarsal of the first toe.
The Old World porcupines, constituting the family Hystricidae, are terrestrial, stoutly built rodents, with limbs of subequal length in front and behind, and the skin covered with strong spines.
All the New World porcupines, representing the family Erethizontidae (or Coendidae) are arboreal in their habits, and have the upper lip undivided, the cheek-teeth rooted, the clavicles complete, the soles of the feet tuberculated and three pairs of teats.
Although showing some dental characters approximating to the porcupines, these rodents are regarded as allied to the Castoridae, although forming an isolated type.
The silk to be opened is placed on a latticed sheet or feeder, and thus slowly conveyed to a series of rollers or porcupines (rollers set with rows of projecting steel pins), which hold the silk firmly while presenting it to the action of a large receiving drum, covered with a sheet of vulcanized rubber, set all over with fine steel teeth.
Squirrels, racoons, woodchucks and skunks are common, and musk-rats, porcupines and opossums are found in some sections.
Squirrels, flying-squirrels, porcupines, civet-cats, rats, bats, flying-foxes and lizards are found in great variety; snakes of various kinds, from the boa-constrictor downward, are abundant, while the forests swarm with tree-leeches, and the marshes with horse-leeches and frogs.
Two or three species of vole (Arvicola) have been detected, and porcupines are common.
There are some porcupines, red foxes, minks and martens, but the moose, wolf and lynx are practically extinct.
Porcupines enjoy a very wide range, being represented throughout the warmer parts of the Old World, with the exception of Madagascar (and of course Australasia), by the Hystricidae, and in the New World by the Erethizontidae.
Ant-eaters (Orycteropus capensis), porcupines, weasels, squirrels, rock rabbits, hares and cane rats are common in different localities.
The genus Atherura includes the brush-tailed porcupines which are much smaller animals, with long tails tipped with bundles of flattened spines.