273 



M. 2297. Cast of a mandibular ramus with seven cheek-teeth of a 

 species belonging to the present section. The original, 

 which is from the Stonesfield Slate, is preserved in the 

 Museum at Oxford, and is figured by Phillips (with an 

 added molar) in his ' Geology of Oxford and the Valley 

 of the Thames,' p. 234, diagram No. 79, under the name 

 of Amphiiherium prevosti. There are three premolars and 

 a diastema behind the canine ; the fourth cheek-tooth may 

 be mm. 4. Same history. 



SECTION B. The true molars usually differentiated into a bilobed 

 blade (which may have a small inner cusp) and a hind talon ; 

 four premolars present in all the English genera of which the 

 entire lower dentition is known ; and generally four lower 

 incisors. 



Those forms which have an inner cusp to the blade of the lower 

 true molars approximate to the Didelphyidce. It is probable that 

 several of the American genera included by Marsh ' in his Dryolestidce 

 belong to the present section ; Dryolestes* itself being apparently 

 very close to Amblotherium. In Astlienodon 3 , which Marsh regards 

 as connecting Dryolestes with Stylodon, the lower true molars have 

 no distinct hind talon. 



Genus AMPHITHERIUM, Blainville *. 



Syn. Amphigonus, Agassiz 8 . 



Thylacotherium, Valenciennes 6 (in parte). 



It is uncertain, owing to the imperfect nature of the type specimen, 

 whether this genus (as restricted by Osborn 7 ) should be referred to 

 the present or the preceding section ; if, however, No. 36822 be 

 rightly referred to it, it undoubtedly belongs to the present one. 



Amphitherium prevosti, Blainville s (ex Cuv. MS.). 



Syn. Didelphis prevosti, Blainville 9 . 



Thylacotherium prevosti, Valenciennes 10 . 



This is now taken as the type species of the genus, and is of minute 

 size u . 



Hob. Europe (England). 



Amer. Journ. ser. 3, vol. xxxiii. p. 334 (1887). 

 Ibid. pi. ix. fig. 2. 3 Ibid. pi. ix. fig. 7. 



Comptes Eendus, Vol. vii. p. 417 (1838). 

 Neues Jahrb. 1835, p. 185. 



Comptes Eendus, vol. vii. p. 580 (1838). 7 See note 1, p. 271. 



Comptes Rendus, vol. vii. p. 403 (1838). Didelphys. * Loc. cif. 



1 Comptes Renclus, vol. vii. p. 580 (1838). 

 Originally Phascolotheriiim was included. 

 PAKT v. * 



