376 MARSUPIALS. 



which forms one of the ancient Mammalia that have rendered the 

 ooUtic formations at Stonesfield so celebrated. This genus, which I 

 have called Phascolotherium, presents the same numerical dental 

 formula as in Phascogale, viz. : 



Incisors — - or 4.4 ; camnes -— ; premolars — : molars — . 



3-3 ' 1—1 ' i 3_3 ' 4_4 



But the incisors and canines are separated by vacant interspaces, 

 and occupy a large proportional space in the dental series (PI. 99, 

 fig. 4). The transition from the false to the true molars is more 

 gradual : the latter are more compressed than in the Opossum ; 

 they present a large middle cusp with a smaller one in front and 

 behind it, and with a basal ridge, which, projecting a little beyond 

 both the anterior and posterior smaller cusps, gives a quinque-cuspid 

 character to the crown of the tooth. 



151. Entomophaga. — This is the most extensive and varied of 

 the primary groups of the Marsupial order. In the system of Cuvier, 

 the species of this tribe are united with those of the preceding to 

 form a single family characterized by the presence of long canines 

 and small incisors in both jaws : but in most of the Entomo- 

 phagous genera of the present classification, the canines present 

 a marked inferiority of development, and the species are conse- 

 quently unable to cope with animals of their own size and grade 

 of organization, but prey, for the most part, upon the smaller and 

 weaker classes of invertebrate animals. Their intestinal canal is com- 

 plicated by a moderately long and large csecum ; and while, in the 

 Sarcophaga, the feet are constructed upon the plan of those of the 

 ordinary placental Digitigrades, they offer in the present tribe a 

 variety of well-marked modifications, according to which the species 

 may be arranged into gressorial, saltatory, and scansorial groups. 



a. GRESSORIA. 



Genus Amphitherium{\) . — This, which includes the oldest known 

 Mammalian inhabitants of our planet, is founded upon fossil remains 

 of jaws and teeth discovered in the Oolite slate at Stonesfield in 



()) See Geological Transactions, 2nd Series, vol. vi, and History of British Fossil Mam- 

 malia, 8vo. 1844. 



