EXTINCT DIPROTODONTS.--The great _Diprotodon_ is a creature with a skull a yard long, which must have been of the size of a large Rhinoceros. Though closely allied to _Macropus_, it seems that this great beast did not hop after the fashion of a Kangaroo, its limbs being of a more equal size than in the Kangaroo. Recently some further remains of _Diprotodon_ have been discovered in a lake known as Lake Mulligan, where they had apparently been bogged. Professor Stirling has contributed an account of these remains, which fills up a considerable gap in our knowledge. He has been able to state the structure of the fore- and hind-limbs. Both limbs are pentadactyle, the fingers of the fore-limb being approximately equal in length and general development. In the hind-limb the hallux is small, and consists of the metatarsal only. This bone is fixed in the position of "extreme abduction," and is suggestive of an arboreal limb. Digits two and three may have {147} been syndactylous, and the authors of the account[91] of these bones think that the fourth toe may have shared in this syndactyly. The metatarsal of the fifth digit is enormously expanded at its edge, and seems to have furnished a strong support to the creature; this is also seen in the metacarpal of the fore-limb. Probably, therefore, _Diprotodon_ was quadrupedal in its mode of progression, with the emphasis laid upon the little finger and the little toe instead of, as in ourselves, the first toe. The hind-foot of the _Diprotodon_ could not be more unlike that of a Kangaroo than it actually is. [Illustration] [Illustration] FIG. 73.--_Diprotodon australis._ (After Owen.) FIG. 74.--_Thylacoleo carnifex._ Side view of skull. (After Flower.) Another giant among these Marsupials was the genus _Thylacoleo_, whose name was given to it by Sir Richard Owen on the view that it was a Marsupial Tiger. Sir W. Flower has, however, controverted this opinion, and the genus is in fact, in spite of its large size, closely allied to the Phalangers and {148} Cuscuses.[92] The dental formula is I 3/1 C 1/0 Pm 3/1 M 1/2; the last premolar is a great blade-shaped tooth like that of _Potorous_. _Nototherium_ was a creature smaller than _Diprotodon_, but still of large size; it is believed to have been a burrowing creature, and to connect the Wombats with _Diprotodon_. More certainly allied to the existing Wombat was _Phascolonus_, a Wombat as big as a Tapir. [Illustration] FIG. 75.--_Nototherium mitchelli._ Side view of skull. x 1/6. (After Owen.) Of extinct American Diprotodonts the Epanorthidae, already referred to in connexion with the living _Caenolestes_, were the most prominent forms. The genus _Epanorthus_ occurs in the Santa Cruz formation of Patagonia, which is believed to be Miocene. The incisors are three in the upper jaw; and the single incisor of each ramus of the lower jaw is a great chisel-shaped, cutting instrument.