FOSSIL MAMMALIA PROM THE STONESFIELD SLATE. 415 



level of the more anterior external cone, and a " basin," if 

 it can be said to exist at all, is small and shallow as far as I 

 have been able to ascertain.^ It should be noticed that this 



Fig. 1 



Fig. 2. 



a.i.c. 



Fig. 1. — Inner face of a molar of the right ramus of the lower jaw of Am- 



phitherium Prevostii. 

 Fig. 2. — Hypothetical representation of the outer face of the corresponding 



molar of the left ramus. a. i. c. Anterior internal cusp (paracone). 



ex. c. External cusp (protocone). h. Heel. ?«. t. e.^ Median internal 



cnsp (metacone). 

 The teeth are represented as if entirely freed from the matrix. 



is the first complete tooth of the tritubercular- 

 sectorial type which has been seen in the Stonesfield fossils. 



Amphitherium Oweni, Osborn. 



The type specimen in the Oxford Museum; a right 

 ramus with the external surface exposed (PI. 26, fig. 3). 



The type and only specimen of this species, obtained with 

 the other jaws from Dr. Buckland's collection, was found pro- 

 bably about 1845. It was first described and figured by Owen 

 in his 'History of British Fossil Mammalia' in 1846 (20), 

 and subsequently in his Monograph (23) and Odontography 

 (21) under the name of A. Prevostii. This specimen, perhaps 

 the most perfect of all the Stonesfield jaws, shows very clearly 

 the angle which, according to Owen, exhibits a degree of inflec- 

 tion which is "less than in any of the known Marsupialia, and 

 does not exceed that of the Mole or Hedgehog'' (20). He 

 describes the six posterior molars as quinquecuspidate, but 



• Judging from other jaws, we may presume that the heel is, if anything, 

 better developed in the anterior molars. 



VOL. 35, PAKT 3. — NEW SER. F F 



