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NATURAL SCIENCE. 



teeth and jaws alone under the name of Homalodontotherunn . From 

 the new discovery we now learn that this animal was a near ally of 

 that peculiar aberrant Perissodactyle known since the date of 

 Darwin's voyage as Macrmichenia. Very important information is 

 also afforded as to the structure of those still more aberrant Un- 

 gulates known as Nesodon, which are nearly related to the huge Toxodon. 

 It is now ascertained that the deciduous and permanent dentitions 

 of these animals were very unlike one another ; in consequence of which 

 many species and even genera have been founded upon ihe remains of 

 one and the same kind of creature. The most remarkable feature about 

 the dentition of Nesodon is to be found in the circumstance that, while 

 the first and second pairs of upper incisor teeth are very large and 

 situated in the same transverse line, the third pair are small and 

 placed in the antero-posterior line of the cheek-teeth, such a feature 

 being quite unknown elsewhere among mammals. 



We might go on almost indefinitely on the subject of these and 

 other strange Ungulates from the Argentine, but we must pause to 



Fig. 4. — Front view of mandibular symphysis and 

 inner side of right mandibular ramus of Homnncvhis 

 pafagonictis — natural size. 



6 c 



c E 



call attention to the great event of the year in the mammalian 

 palaeontology of these regions. Most of our readers are probably 

 aware that, with the exception of the Opossums of America, the 

 Marsupials are confined to Australia and some of the neighbouring 

 islands. Hitherto, no fossil Marsupials of Australian types have been 

 found in Tertiary deposits of any other parts of the world. Now, 

 however, we have the discovery in the Lower Tertiaries of Patagonia 

 of remains of Marsupials nearly allied to the carnivorous Thylacine 

 of Tasmania, and the Dasyures which inhabit both that island and the 

 Australian continent. These have been described under the names of 

 Amphiprovivevra and Pvothylacimts. 



This remarkable and unexpected discovery must profoundlj' 

 modify the views hitherto obtaining as to the former distribution of 

 Marsupials ; and, taken in connection with other circumstances, seems 

 indicative of a former more or less continuous land-connection between 

 the southern extremities of America, Africa, and Australia. Not less 

 important is the connection exhibited by these Patagonian Marsupials 

 with the primitive Tertiary Carnivores of North America and Europe 

 termed Creodonts ; and this leads Dr. Ameghino to conclude that the 



