MARSUPIALIA 303 



is founded upon a few specimens of lower jaw, one ramus of 

 which (fig. 85) gave the entire dentition of its side, — viz., three 

 small conical incisors (i), one rather larger canine (c), six pre- 

 molars, unicuspid, with a small point at one or both sides of 

 the base (jp, 1-6), and r dP^V} 



six quinque-cuspid p >» -•.': v .-'•:, » 



molars (m, i-6) not ^j£l&i&£^- - ' *V* * " 

 departing very tar ^^Sfe^^^fhi^^-p^^^^".- . >z-/ 

 from the type above ;; ' "_" 



described. The mo- Lower .^ and teeth of tbe Amp j l i t j ier i um p re vostii 

 lars, and most of the (twice nat. size.) 



premolars, are implanted by two roots. The condyle of the 

 jaw is convex, and is a little higher than the level of the teeth ; 

 the coronoid process is broad and high ; the angle projects 

 backward, with a feeble production inward. It is, again, to 

 the marsupial Myrmecobius, amongst living forms, that the 

 present genus is most nearly allied. The remains of Amphi- 

 thcrium are from the lower oolitic slates of Stonesfield (fig. 87, 

 stratum 8). 



Genus Amphilestes* — This genus is founded on a ramus 

 of the lower jaw, from the Stonesfield oolitic slate, showing- 

 true molars of a compressed form, with a large middle cusp and 

 a smaller, but well marked, one at the fore and back part of its 

 base ; the " cingulum," or basal ridge, peculiar to mammalian 

 teeth, traverses the inner ridge of the crown, where it develops 

 three small cusps, one at the base of the large outer or princi- 

 pal cusp, and the other two forming the anterior and posterior 

 ends of the crown. This form of tooth is unknown in existing 

 Mammalia, but is as well adapted for crushing the cases of 

 coleopterous insects (elytra of which are found fossil in the 

 same oolitic matrix) as are any of the multi-cuspid molars of 

 small opossums, shrews, and bats. The AmyMhstes Broclcripil 

 was somewhat larger than Amphitlicrium Prevostii. 

 * Owen, Hist. Brit. Foss. Mam., p. 58, fig. 19 (AmpMiherium Broderipii). 



