534 MARSUPIALIA. 



their dentition to the true Carnivora as well as to the Insecti- 

 vora, which they resemble in the large number of their small 

 incisor teeth and tuberculated molars. 



The marsupials are in the main confined to the Australian 

 region, but two families, the Didelphyidae and Epanorthidae 

 {Caenolestes), are found in the neotropical region to which they 

 are peculiar, and the genus Phalanger extends into the island of 

 Celebes, where it is represented by two peculiar species. 



The group is divided into eight families with about 180 species. 



The geological history of the group is interesting. In Aus- 

 tralia, which is now its chief home, no fossil remains are found 

 prior to the Pleistocene, In America, in which both divisions 

 are represented by living forms, remains both of polyprotodonts 

 and diprotodonts are found as far back as the Eocene, and in 

 the case of the Epanorthidae in the Upper Cretaceous. Didel- 

 phyds are found in the Tertiaries of Europe, and there is a 

 number of fossil forms in the Jurassic Formation of Europe 

 and N. America, which are ascribed to the polyprotodont divi- 

 sion (p. 539), Finally there are the Allotheria or, as they are 

 sometimes called, the Multituberculata (p. 541), remains of 

 which are found fossil in the mesozoic rocks of Europe and 

 N. America, and the exact systematic position of which is still 

 very uncertain. 



Sub-order 1, Diprotodontia. 



Incisors three above (one in Phascolomyidae) and one below 

 (small second and third incisors sometimes present in Pha- 

 langeridae), the latter long and powerful. Canines usually 

 small, usually absent below. Molars bluntly tuberculate or 

 ridged. With two sjmdactylous toes except in Caenolestes. 

 Herbivorous, rarely insectivorous. Living forms confined to the 

 Australian and neotropical regions, but found fossil in the 

 Pleistocene of Australia and in the Eocene and Upper Cretaceous 

 of Patagonia and N. America. 



Fam. 1. Macropodidae. Terrestrial, rarely arboreal ; hind limbs 

 longer than the fore, progression generally saltatorial ; manus with 5 

 digits ; pes syndactylous, with 4 digits, the hallux being absent (except 

 in Hypsiprymnodon), fourth toe very large. Tail long, carried hori- 

 zontally backwards in progression ; stomach sacculated ; caeciun present ; 

 pouch opening forwards. Dentition i \ c ^-^ P i m ^ ; the milk pre- 

 molar is long persistent and molariform, the first premolar is shed with 



