{159} We may regard as family-characters the pentadactyle limbs, the existence of three pairs of incisors in the lower and four in the upper jaw; and the tritubercular nature of the upper molars. _Notoryctes typhlops_, the "Marsupial Mole" as it has been termed, was originally discovered by Professor Stirling in Central South Australia. It is a burrowing creature, clothed in a silky fur of a pale golden red, without external ears. It has been compared in appearance with _Chrysochloris_, the Cape Golden Mole, and the eminent palaeontologist, Professor Cope, has even insisted upon a real genetic affinity. Edentate affinities have also been suggested. But _Notoryctes_ has a small pouch opening backwards as in other Polyprotodonts,[98] and as it also possesses marsupial bones it must undoubtedly be referred to the Marsupialia. The animal shows many curious adaptations to its underground mode of life. Certain of the vertebrae in the neck and in the lumbar region are firmly welded together, giving of course a strength of push, and suggesting the Armadillos; the claws of the third and fourth front-toes are greatly enlarged, and must be efficient digging organs. The track of the animal is like that of a railway in mountainous country; it burrows for a short distance, emerges, and then descending beneath the surface re-emerges. The red colour of the fur is said to be in harmony with the arid soil in which it lives. The native name of the creature is "Urquamata." It feeds upon ants and other insects. [Illustration] FIG. 88.--Australian Marsupial Mole. _Notoryctes typhlops._ x 1/4. EXTINCT POLYPROTODONTS.--Of extinct Polyprotodonts (apart from those Mesozoic forms which are considered on p. 100) extinct species of _Thylacinus_ and _Dasyurus_ are known from {160} Australia. The most interesting fact in connexion with the Tertiary Polyprotodonts is the existence in South America of such genera as _Prothylacinus_ and _Amphiproviverra_, which are not merely Polyprotodonts but definitely Dasyures, and not referable to the Didelphyidae.