AARD-WOLF (earth-wolf), a South and East African carnivorous mammal (Proteles cristatus), in general appearance like a small striped hyena, but with a more pointed muzzle, sharper ears, and a long erectile mane down the middle line of the neck and back.
Paired erectile plates (patagia) are borne on the prothorax in moths, while in moths, sawflies, wasps, bees and other insects there are small plates (tegulae) - see Fig.
From the North American grey foxes, constituting the genus or subgenus Urocyon, the true foxes are distinguished by the absence of a crest of erectile long hairs along the middle line of the upper surface of the tail, and also of a projection (subangular process) to the postero-inferior angle of the lower jaw.
The American grey fox, or Virginian fox, is now generally ranged as a distinct genus (or a subgenus of Canis) under the name of Urocyon cinereo-argentatus, on account of being distinguished, as already mentioned, by the presence of a ridge of long erectile hairs along the upper surface of the tail and of a projection to the postero-inferior angle of the lower jaw.
Its appearance is sufficiently striking - the head and lower parts, except a pectoral band, white, the former adorned with an erectile crest, the upper parts dark grey banded with black, the wings dusky, and the tail barred; but the huge bill and powerful scutellated legs most of all impress the beholder.
Although firmly anchylosed to the bone, the tooth, which when at rest is laid backwards, is erectile, - the bone itself being mobile and rotated round its transverse axis.
The Viperidae alone have "erectile" fangs.
Maxillary vertically erectile, perpendicularly to ectoptery goid, and reaching quadrate or mandible: Viperidae.
Eyes free; with a pair of poison-fangs in the front part of the mouth, carried by the otherwise toothless, much shortened, and vertically erectile maxillaries; ventral scales transversely enlarged: Viperidae.
The mucous membrane is raised into a series of transverse folds or rugae, and between it and the muscular wall are plexuses of veins forming erectile tissue.
The bulbs of the vestibule are two masses of erectile tissue situated one on each side of the vaginal orifice: above they are continued up to the clitoris; they represent the bulb and the corpus spongiosum of the male, split into two, and the fact that they are so divided accounts for the urethra failing to be enclosed in the clitoris as it is in the penis.
The penis is the intromittent organ of generation, and is made up of three cylinders of erectile tissue, covered by skin and subcutaneous tissue without fat.
Along the middle of the hinder half of the back is a line of long erectile white hairs, forming the "fan," continued down over the rump; in repose this is concealed by the surrounding hair, but is conspicuously displayed when the animal takes the great leaps from which it derives its popular name.
Furthermore, there is a common littoral fish in the Mediterranean (Uranoscopus scaber), belonging to the same family as Trachinus, exhibiting the same habits and living on the same ground, which also has a jet black erectile dorsal fin, and is believed to be poisonous.
The most distinctive feature of the deer of this group is, however, the patch of long erectile white hairs on the buttocks, which, although inconspicuous when the animals are quiescent, is expanded into a large chrysanthemum-like bunch when they start to run or are otherwise excited.