It may also be comparable to the great premolar of such Multituberculata as Ptilodus and Plagiaulax. It is, moreover, marked with vertical grooves.
An interesting form, which is unfortunately but little known, is the Australian and Pleistocene genus Triclis, with one species, T. oscillans. In having a minute canine tooth in the lower jaw it agrees with some Phalangeridae, and being otherwise closely allied to Hypsiprymnodon, it unites the Macropodidae with the Phalangeridae.
Sub-Order 2. POLYPROTODONTIA.
In this mainly carnivorous or insectivorous division of the Marsupials the incisors are four or five on each side of the upper jaw, and one or two fewer in the lower jaw. Figs. 76 and 77 illustrate the Polyprotodont and Diprotodont dentitions. The canines are those of flesh-eaters and so are the molars, being as a rule sharply cuspidate. As a rule, which has an exception in the Peramelidae, there is no syndactylism of toes in the hind-foot. This sub-order is at the present day Australian and American in its range.
Fig. 76.—Front view of the skull of Tasmanian Devil (Sarcophilus ursinus), showing Polyprotodont and carnivorous dentition. (After Flower.)
Fam. 1. Dasyuridae.—This family consists of Marsupials which are generally pentadactylous, but with occasionally the hallux missing. The tail is long but not prehensile. The pouch is present or absent. The teeth vary in the different genera, but
