The remaining and more typical members of the family, one of which is aquatic, are characterized by their short incisors, the strong masseteric ridges on the sides of the lower jaw, the long and curved par-occipitals and the palate contracted in front.
Associated with this is the strength and sharpness of the lower jaw, the prominence and anterior pcsition of the masseteric ridge, and the depth of the ramus from the alveolar line to the angle.
The masseteric ridge of the lower jaw is obsolete, the palate broad, the incisors long and the molars semi-rooted, with external and internal enamel-folds (see Agouti).