540 MARSUPIALIA. 



often with bifid root ; premolars and molars with 3 cusps in a row (tri- 

 conodont), with a strong cingulum and with bifid roots ; angle of mandible 

 inflected. Jurassic of England and N. America. Triconodon Owen, 

 Middle Purbeck Beds of Dorsetshire and U. Jurassic of Wyoming. Am- 

 philestes * Owen, Stonesfield Slate. Phascolotherium Owen, Stonesfield 

 Slate. Spalacotherium Owen, Purbeck, Dorsetshire, lower molars with 

 .one large outer cusp and two small inner cusps (tritubercular), resem- 

 bling those of some Insectivora ; dentition of mandible i3cl p 4 m 6. 

 Priacodon, Marsh, etc. IJ. Jurassic, Wyoming. 



Fam. 7. Amphitheriidae.t With numerous two- or three-rooted tritu- 

 berculated lower molars with a heel (so-called tubercular-sectorial, Fig. 

 283), resembling those of the opossums, bandicoots, some insectivores, 

 and the lower carnassial teeth of Carnivora ; the main cusp (inner in the 

 upper jaw, outer in the lower) is connected with the two other cusps 

 by crests ; premolars with three cusps in a row and with cingulum ; canines, 

 usually two-rooted ; angle of mandible often slightly inflected. Jurassic 

 and Cretaceous. Amphitherium Blv., Stonesfield Slate ; the lower jaw 

 upon which this genus is based was together with that of Phascolotherium, 

 the first of the remains of Mesozoic Mammalia discovered. The specimens 



a.Lc. 



FIG. 283. a Inner face of a molar of the right raraus of the lower jaw of Amphitherium pre- 

 voslii. b Hypothetical representation of the outer face of the corresponding tooth of the 

 left ramus (after Goodrich), a.i.c. anterior internal cusp (paracoue), ex.c external cusp 

 (protocone), h heel, m.i.c. median internal cusp (metacone). 



were brought to Mr. W. J. Broderip of Oxford about the year 1814, 

 and one of them was acquired by Professor Buckland and placed in the 

 Ashmolean Museum ; it is now in the Oxford University Museum ; 

 dentition of lower jaw i 4 c 1 p 5 m 6 ; angle of mandible slightly 

 inflected ; mylohyoid groove conspicuous. Peramus Owen, U. Jurassic of 

 England. Amblotherium Owen, Purbeck, Dryolestes Marsh, Upper Jurassic 

 and Upper Cretaceous of N. America. 



The Sparassodontidae (Borhyaenidae) present resemblances to the 

 carnivorous marsupials of Australia, and may be placed near the Dasyu- 

 ridae, which they resemble in their dentition. They are of considerable 

 or moderate size with a dentition of i j-^| c \ p j-jjj-j m ; the 

 canines (well-developed) and two premolars only are known to have 

 been replaced ; the upper molars are tritubercular, the lower cutting ; 

 there are no marsupial bones and the characteristic marsupial palatal 

 vacuities are absent ; the angle of the mandible is strongly inflected. By 



* Goodrich, Q.J.M.S., 35, 1894, p. 407. 

 t Goodrich, op. cit. 



