Finally, we have the family Rhinocerotidae, which includes the existing representatives of the group. In this family the dentition has undergone considerable reduction, and may be represented inclusive of all the variations, by the formula i a or a m a The first upper incisor, whenpresent, has an 430r2; PP antero-posteriorly elongated crown, but the second is small; when fully developed, the lower canine is a large forwardly directed tusk-like tooth with sharp cutting-edges, and biting against the first upper incisor.
These forwardly-slipped somites are called " prosthomeres."
Reedbuck, or rietbok (Cervicapra), are foxy-red antelopes ranging in size from a fallow-deer to a roe, with thick bushy tails, forwardly curving black horns, and a bare patch of glandular skin behind each ear.
In the Achorutidae the head is forwardly directed, the tergum of the prothorax conspicuous, and the spring small or vestigial.