262 HISTORICAL PALAEONTOLOGY. 



184) are also believed by the same distinguished anatomist 

 and palaeontologist to have been insect-eating Marsupials, and 

 the latter is supposed to find its nearest living ally in the 

 Opossums (Didelphys) of America. Lastly, the Stereognathus 

 of the Stonesfield Slate is in a dubious position. It may have 

 been a Marsupial; but, upon the whole, Professor Owen is 

 inclined to believe that it must have been a hoofed and her- 

 bivorous Quadruped belonging to the series of the higher Mam- 

 mals (Placentalid) . In the Middle Purbeck beds, near to the 

 close of the Oolitic period, we have also evidence of the exist- 

 ence of a number of small Mammals, all of which are probably 

 Marsupials. Fourteen species are known, all of small size, 

 the largest being no bigger than a Polecat or Hedgehog. The 

 genera to which these little quadrupeds have been referred are 

 Plagiaulax, Spalacotherium, Triconodon, and Galestes. The 

 first of these (fig. 184, 4) is believed by Professor Owen to 

 have been carnivorous in its habits ; but other authorities 

 maintain that it was most nearly allied to the living Kangaroo- 

 rats (Hypsipry ninns} of Australia, and that it was essentially 

 herbivorous. The remaining three genera appear to have 

 been certainly insectivorous, and find their nearest living rep- 

 resentatives in the Australian Phalangers and the American 

 Opossums. 



Finally, it is interesting to notice in how many respects the 

 Jurassic fauna of Western Europe approached to that now 

 inhabiting Australia. At the present day, Australia is almost 

 wholly tenanted by Marsupials ; upon its land-surface flourish 

 Araucaria and Cycadaceous plants, and in its seas swim the 

 Port-Jackson Shark (Cestracion Philip pi} ; whilst the Mollus- 

 can genus Trigonia is nowadays exclusively confined to the 

 Australian coasts. In England, at the time of the deposition 

 of the Jurassic rocks, we must have had a fauna and flora very 

 closely resembling what we now see in Australia. The small 

 Marsupials, Amphitherium, Phascolotherium, and others, prove 

 that the Mammals were the same in order; cones of Arau- 

 carian pines, with tree-ferns and fronds of Cycads, occur 

 throughout the Oolitic series; spine-bearing fishes, like the 

 Port-Jackson Shark, are abundantly represented by genera 

 such as Acrodus and Strophodus; and lastly, the genus Tri- 

 gonia, now exclusively Australian, is represented in the Oolites 

 by species which differ little from those now existing. More- 

 over, the discovery during recent years of the singularMud-fish, 

 the Ceratodus Fosteri, in the rivers of Queensland, has added 



