MONOTREMATA AND MARSUPIALIA. 



291 



to Myrmecobius. Each ramus of the lower jaw contains 

 " ten small molars in a continuous series, one canine, and 



Fig. 601. — Lower jaw o( DromaMerium syluesire. 

 Trias, North Carolina. (After Emmons.) 



Fig. 602.— a, Molar tootli of 

 Microlestes OMtiquus, magnified ; 

 b. Crown of the same, magnified 

 still farther. Trias, Germany. 



three conical incisors — the latter being divided by short 

 intervals" (Owen). 



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 be- 

 long to small Marsupials. Four genera of small Mammals 

 are known from this horizon — viz., Ampliilestcs, Amphither- 

 imn, Phascolotherinmi, and Stcreognaihus. In Amphithermm 

 (fig. 603) the molars are cuspidate, and the animal was 

 doubtless insectivorous. It 

 is believed by Owen to be 

 Marsupial, and to be most 

 nearly related to Myrmc- 

 cohius. Amphilestes and 



PhaSCOIotlierium (fig. 604, Fig, eOS.— Ramus of the lower jaw of ^mp/a-- 



1) are also believed by *^^^'^ (TliylacomerUcm:) PrevostU. Stonesfield 



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 Siereognathus of the Stonesfield 

 Slate is in a dubious position. It may have been Mar- 

 supial ; but, upon the whole, Prof. 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 al- 

 most wholly tenanted by Marsupials ; upon its land-surface 

 flourish Araucarice and Cycadaceous plants, and in its seas 



