form of the bulla is Aeluroid. The teeth vary somewhat in number, and the following table will serve to indicate the gradual reduction observable in the number of molars:—
| Otocyon | I 3/3 C 1/1 Pm 4/4 M (3 or 4)/4 |
| Canis generally | I 3/3 C 1/1 Pm 4/4 M (3 or 2)/(4 or 3) |
| Cyon | I 3/3 C 1/1 Pm 4/4 M 2/2 |
| Icticyon | I 3/3 C 1/1 Pm 4/4 M (2 or 1)/2 |
All the Dogs have a caecum[1] of simple cylindrical form. In C. cancrivorus, C. jubatus, and Nyctereutes procyonides this organ is straight or only very faintly curved; in other Dogs it is coiled into an 
-like form, sometimes with an additional twist. The Dogs have, as a rule, five toes, one being dropped in Lycaon. The tail is fairly long and distinctly bushy. There is in a number of species a gland at the root of the tail, the presence of which can frequently be detected by the wet appearance due to the oozing secretion. The great majority of existing Canidae belong to the genus Canis. But certainly three, and more doubtfully four, other genera can be distinguished.
The genus Icticyon contains but one recent species, the Bush Dog (I. venaticus, Lund) of British Guiana. The animal has a somewhat Paradoxure-like, at any rate a distinctly un-dog-like, aspect, being longish in the body (some 2 feet long), shortish in the legs, and big-headed. It is blackish in colour, verging towards golden brown on the head and back. Sir W. Flower, to whom we owe our chief knowledge of its structure, characterises it as like a young Fox, and with the playful manners of a puppy. The animal appears to hunt in packs and by scent, and has a reputation for ferocity. Icticyon differs from Canis and agrees with the Indian Cuon in having but forty teeth, the last molar having disappeared from the upper and lower jaws. The caecum, unlike that of the majority of Canidae, is only slightly curved. The brain, oddly enough, shows a Cat-like peculiarity. It has been pointed out that in their long bodies and short legs the genera Cuon and Icticyon resemble the primitive dogs.[2]
A genus Nyctereutes is usually separated from Canis for the inclusion of N. procyonides only. The separation is based upon
