The COMMON PORCUPINE (_Hystrix cristata_) may serve as a characteristic and well-known example of the first of these two groups. It is an inhabitant of the Mediterranean region, occurring in most parts of North Africa, and extending as far southwards as the Gambia and Soudan; in Southern Europe it is abundant in Italy, Sicily, and Greece. It measures about twenty-seven or twenty-eight inches in length to the root of the tail, which is about four inches long. The head, shoulders, limbs, and under parts are clothed with short spines intermixed with hairs usually of a dusky or brownish-black hue; the neck is marked with a whitish collar; from the back of the head and neck there rises a great crest of long bristles, many of them fifteen or sixteen inches in length, which can be elevated and depressed at the pleasure of the animal, are gently curved backwards, and are either dusky with the extremities white, or whitish throughout; the hinder portion of the body is entirely covered by a great number of long, sharp spines, ringed with black and white, but always having the extremities white. These spines vary considerably in size, some of them being very long (fifteen or sixteen inches), comparatively slender and flexible; others shorter (from six to twelve inches), but much stouter. They are all hollow, or filled only with a sort of spongy tissue, but from their structure are exceedingly resistant, and when the animal erects them, which he is able to do by contracting the muscles of the skin in which their roots are imbedded, they constitute a most formidable armature. They appear to be but loosely attached to the skin, and readily fall out, a circumstance which no doubt gave rise to the belief prevalent among the ancients (and many moderns) that the Porcupine was able to shoot his spines at an approaching enemy, or even to project them behind him at a pursuer when he was rushing away in search of a place of safety. The tail of the animal bears at its tip about twenty spines of very curious construction; they are about two inches long, hollow, open, and cut off square at the end, and about a quarter of an inch in diameter for the greater part of their length, but they are inserted into the skin by the extremity of a thin stalk half an inch long.