Macropodidæ.

Numerous species of all sizes, some several times larger than any modern Kangaroo, existed in Australia in former ages, but their remains are much scattered about, and upper and lower jaws are seldom found together; to distinguish the bones as those of particular species is out of the question, and we must content page 20 ourselves at present to class them as Kangaroo, or Kangaroo-rat bones. The fossils which resemble, or are identical with, modern species, may of course be more correctly classified.

As a general rule, most of the fossil Kangaroos have shorter and stouter tarsi than living species possess, and the greater number, including the largest of the tribe, must be arranged with the Halmaturi or Wallabies, a group of Kangaroos with permanent and often large premolar teeth.

The Kangaroos proper, of which our common Great Kangaroo is the type, soon shed their premolars, and continue to lose the grinders also in such a manner that sometimes only a pair of teeth are left in each ramus. The Wallabies, on the other hand, wear the teeth down. Looking at a Kangaroo's incisors, we find the first of the upper series comparatively small, and the third very broad; whilst the Wallabies have the third tooth large in a vertical direction, and in most species this tooth is deeply indented by a fold.

In all recent Kangaroos, Wallabies, and Kangaroo-rats, the rami of the lower jaw are movable; in many fossil Kangaroos this peculiar characteristic is wanting, and the two mandibles are firmly anchylosed, as may be observed in the two fossil species Halmaturus Scottii and Halmaturus Thomsonii.

The premolars of the fossil species are often very bulky, with a deep hollow in the middle of the tooth—another characteristic peculiar to extinct animals of this tribe.

The following genera belong to the family Macropodidæ:—

Bettongia.

Comprising the Kangaroo-rats, or more correctly speaking, the "Bettongs," with long hind legs, and more or less prehensile tail. Of these animals many remains were found at Wellington, all of which appear to be identical with the common Bettong Bettongia rufescens, now living in New South Wales.

Hypsiprymnus.

This genus had very few representatives, and comprises the smaller Kangaroo-rats, with short stiff tails and short hind-legs; all Hypsiprymni progress in the same manner as the Bandicoots.

Macropus.

The typical species is our Macropus major or Great Kangaroo. Fossil remains of closely allied species, and of others, resembling M. ocydromus, M. rufus, and M. robustus, are in our collection.

Halmaturus.

This genus, distinguished by permanent and often very large premolar teeth, is numerously represented in a fossil state, and cannot be estimated at less than thirty or more species; the Wombat-like Kangaroos, with short anchylosed jaws, are here included.