4IO ORDERS OF MAMMALIA. 



The next Mammaliferous horizon above the Trias is the 

 Stonesfield Slate in the Lower Oolites ; and there is no doubt 

 that some, if not all, of the Mammalian remains of this belong 

 to small Marsupials. Four genera of small Mammals are 

 known from this horizon viz., Amphilestes, Amphitherium, 

 Phascolotherium, and Stereognathus. In Amphitherium (fig. 

 339), the molars are cuspidate, and the animal was doubtless 



Fig. 339- Ramus of the lower jaw of Amphitheritim(ThylacotIuriuni) 

 Prevostii. Stonesfield Slate. 



insectivorous. It is believed by Owen to be Marsupial, and 

 to be most nearly related to Myrmecobius. Amphilestes and 

 Phascolotherium (fig. 340) are also believed by the same high 

 authority to have been insectivorous Marsupials, and the latter 

 is supposed to find its nearest living ally in the Opossums of 

 America. Lastly, the Stereognathus of the Stonesfield Slate is 

 in a dubious position. It may have been Marsupial ; but, 

 upon the whole, Professor Owen is inclined to believe that it 

 was placental, hoofed, and herbivorous. 



With the occurrence of small Marsupials in England within 

 the Oolitic period, it is interesting to notice how the fauna of 

 that time approached in other respects to that now inhabiting 

 Australia. At the present day, Australia is almost wholly 

 tenanted by Marsupials ; upon its land-surface flourish Arau- 

 carice and Cycadaceous plants, and in its seas swims the Port- 

 Jackson Shark (Cestradon Philippi) ; whilst the Molluscan 

 genus Trigonia is nowadays exclusively confined to the Aus- 

 tralian coasts. In England at the time of the deposition of 

 the Stonesfield Slate, we must have had a fauna and flora very 

 closely resembling what we now see in Australia. The small 

 Marsupials Amphitherium and Phascolotherium prove that the 

 Mammals were the same in order ; cones of Araucarian 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 Trigonia, now exclu- 

 sively Australian, is represented in the Stonesfield Slate by 

 species which differ little from those now existing. 



Another singular point of resemblance is established by the 



