PLAGIAULAX. 355 



is succeeded by four square-crowned double-ridged grinders 

 adapted for vegetable food ; and the position of the condyle, 

 the slenderness of the coronoid, and other characters of the 

 lower jaw, are in conformity to that regimen. In Thylacoleo 

 the lower canine or canine-shaped incisor projected from the 

 fore part of the jaw close to the symphysis, and the correspond- 

 ing tooth in Plagiaulax more closely resembles it in shape and 

 direction than it does the procumbent incisor of Hypsiprymnus. 

 From this genus Plagiaulax differs by the obliquity of the 

 grooves on its premolars ; by having only two true molars in 

 each ramus of the jaw, instead of four ; by the salient angle 

 which the surfaces of the molar and premolar teeth form, 

 instead of presenting a uniform level line ; by the broader, 

 higher, and more vertical coronoid ; and by the very low 

 position of the articular condyle. 



The physiological deductions from the above-described 

 characteristics of the lower jaw and teeth of Plagiaulax are, 

 that it was a carnivorous Marsupial. It probably found its 

 prey in the contemporary small insectivorous Mammals and 

 Lizards, supposing no herbivorous form, like Stereog?iathus, to 

 have co-existed during the upper oolitic period. 



In the Woodwardian Museum at Cambridge is a specimen 

 of anchylosed cervical vertebrae of a cetaceous animal as large 

 as a grampus, but presenting specific distinctions from all 

 known recent and fossil species. It is stated to have been 

 found in the brown clay or " till " near Ely ; but in its petri- 

 fied condition, colour, and specific gravity, it is so different 

 from the true bones of the " till," and so closely like the fossils 

 of the Kimmeridge clay, as to make it extremely probable that 

 it has been washed out of that formation. 



No evidence of the mammalian class has yet been met 

 with in the chalk beds. 



The examples of the Mammalia of the oldest tertiary 



