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Show 182 DR. A. S. WOODWARD ON EXTINCT [Mar. 5, similar teeth during the Cretaceous period in the Northern hemisphere ; but it seems probable that the completion of the tooth-sockets and the paucity of successional teeth in Genyodectes are characters indicating that it was one of the latest and most specialized members of its race. IV. CONCLUSION. The extinct reptiles discovered in the red sandstones of Northern Patagonia are now of special interest from two points of view. Firstly, there is a curious mixture of types which in other parts of the world belong to more than one geological period ; secondly, the occurrence of Miolania seems to confirm the much-discussed theory of an old Antarctic continent and a former connection between South America and Australia. The association of ancient with modern types of reptiles is especially remarkable. The nearest allies of the Crocodile Noto-suchus occur in the Upper Jurassic of Europe, while the latest known Dinosaurs are undoubtedly Upper Cretaceous both in Europe and North America. Miolania, on the other hand, occurs in the latest Pleistocene deposits of Queensland, associated with extinct though typically Australian mammals; while the smaller species of the same genus found in Lord Howe's Island must be regarded as equally modern. Dinilysia, again, is a typical South American Snake, such as might have occupied an appropriate place in the fauna of that continent w hen the gigantic Glyptodonts and Ground- Sloths were flourishing. The anomaly may be explained either (i.) by supposing that the essentially Mesozoic land-reptiles survived to a later period in Patagonia than elsewhere; or (ii.) by assuming that geologists are mistaken concerning the age and apparent contemporaneity of some of the red sandstones of Neuquen and Chubut. The problem must be solved by future geological research. Of all the similarities between the South-American and Australian faunas, perhaps none is more striking than the essential identity of the extinct Miolania in the two regions. There can be no doubt that this was a truly terrestrial or marsh Chelonian; while it seems at first highly improbable that so remarkably specialized a dermal armour as it possessed could be independently acquired by distinct animals in two different regions of the globe. The theory of a former land-connection between South America and Australia seems therefore to receive important support from the new discovery now described. It must, however, be remembered that during the late Mesozoic and early Cainozoic (Tertiary) periods, the Pleurodiran Chelonia had a much wider distribution than at present-were, in fact, perhaps nearly as cosmopolitan as are the Cryptodira in the existing world. It is known that the doubly-armoured Herring Diplomystus, n o w living in the rivers of Chile and N e w South Wales, was a widely distributed marine fish in the |