MARSUPIALIA. 



411 



occurrence in the rivers of Queensland of the " Barramunda," 

 which is referred to the genus Ceratodus a genus which, though 

 pre-eminently Triassic, nevertheless extended its range into 

 the Jurassic period. 



Towards the close of the Oolitic period, in the Middle Pur- 

 beck beds, we have evidence of a number of small Mammals, all 

 of which are probably referable to the Mamipialia. Fourteen 

 species are known, all of small size, the largest being no bigger 

 than a polecat or hedgehog. The genera to which these little 

 quadrupeds have been referred are Plagiaulax, Spalacotherium, 

 Triconodon, and Galestes. The first of these viz., Plagiaulax 

 (fig. 340, 4) is believed to be most nearly allied to the living 



Fig. 340. Oolitic Mammals, natural size. i. Lower jaw and teeth of Phascolotherium ; 

 2. of Triconodon; 3. of A mphitlierium ; 4. of Plagiaulax. 



Kangaroo-rats (Hypsiprymnus) of Australia ; and it is held by 

 good authorities to have been phytophagous, as are its living 

 relatives. Professor Owen, on the other hand, maintains that 

 Plagiaulax was carnivorous. The remaining three genera 

 viz., Spalacotherium, Triconodon (fig. 340, 2), and Galestes ap- 

 pear to have been certainly insectivorous, and find their nearest 

 living allies in the Australian Phalangers and the American 

 Opossums. 



In the older Tertiary Rocks the remains of Marsupials are 

 not abundant. In the Eocene Tertiary (Gypseous series of 

 Montmartre), however, occurs an Opossum, which is very 

 closely allied to the existing American forms, and which has 

 been named the Didelphys Gypsorum. Other species of the 

 same genus have also been discovered in deposits of Miocene 

 age. 



In the later Tertiary and Post-tertiary period the order of 

 the Marsupialia is represented by some very remarkable forms. 

 The remains in question have been found in the bone-caves of 

 Australia the country in which Marsupials now abound above 

 every other part of the globe ; and they show that Australia, 



