122 Zoological Society. 



Mammalia ; and corresponds with the food and habits of the species 

 which thus lead from the Zoophagous to the Entomophagous tribe. 



Other links which once bound these tribes more closely together 

 are now lost, and are indicated only by the few fossil remains 

 which have rendered the Stonesfield oolite so celebrated. One of 

 these extinct genera, which I have called Phascolotherium, presents 

 the same numerical formula, apparently, as in the Thylacinus 

 and Phascorjale ; but, if another incisor existed in each ramus of 

 the lower jaw, as seems to be indicated by the fossil, then the den- 

 tition will agree with that of the genus Didelphis. 



Incisors |^ ; canines |^^ ; prsemolares ^^ ; molares |^. 



or 



4—4 



The incisors and canines are separated by vacant interspaces, 

 and occupy a large proportion of the dental series : the true mo- 

 lares resemble those of Thylacinus, 



Tribe II. 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 group 

 characterized by the presence of long canines and small incisors in 

 both jaws ; but in most of the Entomophagous genera of the pre- 

 sent classification, the canines present a marked inferiority of de- 

 velopment, and the species are consequently unable to cope with 

 animals of their own size and grade of organization, but prey upon the 

 smaller and weaker classes of invertebrate animals. Their intestinal 

 canal is complicated by a moderately long and large caecum ; and, 

 while in the Sarcophaga, the feet are organized, as in the ordinary 

 placental Digiiigrades, they present in the present tribe a variety 

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

 be arranged into ambulatory, saltatory, and scansorial groups. 



Ambulatobia. 

 The only known existing representative of this family is the 

 animal described by Mr. Waterhouse, which constitutes the type of 

 his genus Myrmecohius, of which the following is the remarkable 

 dental formula : 



Incisors ^^ ; canines ~ ; praemolares 3^3 J molares ^^ : = 52. 



From which it will be seen, that the number of molares, sixteen 

 in the upper and eighteen in the lower jaw, exceeds that of any 

 other known existing Marsupial, and approaches that which charac- 

 terizes some of the insectivorous armadilloes. The resemblance to 



