MONOTREMATA AND MARSUPIALIA. 



289 



The Marsupialia are divided by Owen into the two pri- 

 mary groups of the Diprotodontia and Pohjirrotodontia, in 

 accordance with the condition of the incisor teeth. In the 

 Diprotodont forms (fig. 599, a) there are only two lower 

 incisors, canines are rudimentary or wholly wanting; and 

 the molars mostly have broad grinding crowns. The living 

 members of this group — such as the Kangaroos (Macropodidce), 

 the Wombat {Phascolomys), the Kangaroo-rats {Hypsiprymnus), 

 and the Phalangers (Fhalangistidce) — are all herbivorous ; and 



Fig. 599. — A, Dentition ot a Bipiotodout Maisupial (Hypupiyinnus cunicultis), showing 

 the upper canine (c) and the gieat grooved hist prajmolar (a, a) ; b, Lower jaw of an 

 entomophagous Polyprotodout Marsupial {Perameles obesula); c, Lower jaw of a predatory 

 Polyprotodont Marsupial (Dasyums ursimis). (After Giebel and Waterhouse.) 



this is the case with the great majority of the fossil forms, 

 though Prof. Owen is of opinion that some of the latter were 

 carnivorous in habit. In the Polyprotodont Marsupials- — - 

 such as the living Bandicoots {Perameles), Opossums {Didcl- 

 p)hidm), the Banded Ant-eater {Myrmecohius), the Dasyurus, 

 and the Thylacinus — there are always more than two lower 

 incisors (fig. 599, b and c), the canines are more or less ex- 

 tensively developed, and the molars are either cuspidate or 

 have sectorial crowns. All the members of this section are 

 essentially carnivorous, feeding upon insects or upon the 

 VOL. II. T 



