340 



PALEONTOLOGY. 



Fig. 112. 



Lower jaw and teeth of the Amyhitlierium 



Prevostii (twice nat. size). 



in Phascolotherium. The specimen is from the Chatham coal- 

 field, N". Carolina, and is probably of triassic age. 



Genus Amphithekium (Thylacotherium, Val).* — This genus 

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

 which (fig. 112) gave the entire dentition of its side, — viz., three 



.,^~~y--, small conical inci- 



sors (i), one rather 

 larger canine (c), six 

 premolars, unicus- 

 pid, with a small 

 point at one or both 

 sides of the base 

 (p, i-6), and six quinque-cuspid molars (m, i-6) not depart- 

 ing very far from the type above described. The molars, 

 and most of the 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 Myrmecobms, amongst living 

 forms, that the present genus is most nearly allied. The 

 remains of Amphithermm are from the lower oolitic slates of 

 Stonesfield (fig. 114, stratum 8). 



Genus AMPHiLESTES.t — This genus is founded on a ramus 

 of the lower jaw, from the Stonesfield oolitic slate, shewing 

 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 mam- 

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

 develops three small cusps, one at the base of the large outer 

 or principal cusp, and the other two forming the anterior and 

 posterior ends of the crown. This form of tooth is unknown 



* For the full description and demonstration of the mammalian nature of this 

 much-discussed fossil, see Owen, History of British Fossil Mammals, 8vo, p. 29. 

 f Owen, Hist. Brit. Foss. Mam., p. 58, fig. 19 (Amphitlierium Broderipii). 



