From all the other members of the group the _Canidae_ are broadly distinguished (in the case of existing forms) by the large and well-developed tympanic bulla, with which the paroccipital process is in contact. An alisphenoid canal is present. The feet are digitigrade, usually with five (in one instance four) front and always four hind-toes. The molars--generally 2/3--have tall cusps, and the sectorials are large and powerful (figs. 1 and 2). The intestine has both a duodeno-jejunal flexure and a caecum. A prostate gland is present; but there are no glands in the vasa deferentia; the penial bone is grooved; and anal glands are generally developed. The distribution of the family is cosmopolitan. The normal dentition is i. 3/3, c. 1/1, p. 4/4, m. 2/3; total 42; thus differing from the typical series only by the loss of the last pair of upper molars (present in certain extinct forms). In the characters of the teeth the group is the most primitive of all Carnivora. Typically the upper secterial (fig. 1, II) consists of a stout blade, of which the anterior cusp is almost obsolete, the middle cusp large, conical and pointed backwards, and the posterior cusp in the form of a compressed ridge; the inner lobe is very small, and placed at the fore part of the tooth. The first molar is more than half the antero-posterior length of the sectorial, and considerably wider than long; its crown consists of two prominent conical cusps, of which the anterior is the larger, and a low, broad inward prolongation, supporting two more or less distinct cusps and a raised inner border. The second molar resembles the first in general form, but is considerably smaller. The lower sectorial (fig. 2, II) is a large tooth, with a strong compressed bilobed blade, the hinder lobe being considerably the larger and more pointed, a small but distinct inner tubercle placed at the hinder margin of the posterior lobe of the blade, and a broad, low, tuberculated heel, occupying about one-third of the whole length of the tooth. The second molar is less than half the length of the first, with a pair of cusps placed side by side anteriorly, and a less distinct posterior pair. The third is an extremely small and simple tooth with a subcircular tuberculated crown and single root.