VERTEBRATA: MAMMALIA. 



669 



a small Mammal, which is probably Marsupial, and has been 

 named Dromatherium (fig. 368). 



68. Lower jaw of Dromatherium sylvestre. 

 rias, North Carolina. (After Emmons.) 



Fig. 369. a Molar tooth of Micro- 

 lestes antiquus, magnified; b 

 Crown of the same, magnified 

 still further. Trias, Germany. 



In the next mammaliferous horizon, however namely, that 

 of the Stonesfield Slate in the Lower Oolites there is no doubt 

 but that some of the Mammalian remains, if not all, belong to 

 small Marsupials (fig. 370). From this horizon the two genera, 

 Phascolotherium and Amphitherium are almost certainly refer- 

 able to the Marsupialia ; the latter seeming to be most nearly 

 related to the living Myrmecobius, whilst the former finds its 

 nearest living ally in the Opossums of America. The Stereo- 

 gnathus of the Stonesfield Slate is in a doubtful position. It 

 may have been Marsupial ; but, upon the whole, Professor 

 Owen is inclined to believe that it was placental, hoofed, and 

 herbivorous. 



In the middle Purbeck beds (Upper Oolite), where fourteen 

 species of Mammals are known to exist, it is probable that all 



Fig. 370. Oolitic Mammals, natural size. i. Lower jaw and teeth of Phascolotherium 

 2. of Triconodon ; 3. of A mphitherium ', 4. of Flag iaulax. 



were Marsupial. All the Purbeck Mammalia were of small 

 size, the largest being no bigger than a polecat or hedgehog. 

 They form the genera Plagiaulax, Triconodon, and GaZestes, of 

 which Plagiaulax is believed to be most nearly allied to the 

 living Kangaroo-rat (Hypsiprymnus) of Australia. 



In the Tertiary series of rocks Marsupials are of rare occur- 



