170 MARSUPIALIA 



Wallabies, which are small and lightly-built animals, in some 

 instances not larger than a Rabbit. Their muffles are always naked, 

 and in the skull the anterior palatine foramina are small and the 

 posterior vacuities very large, while the posterior expansion of the 

 nasals is very marked. The third upper incisor is smaller than in 

 the last group. This group extends farther into the tropics than 

 either of the others, being found in the New Britain and Aru 

 islands, as well as in New Guinea. M. brachyurus is remarkable for 

 its comparatively short and slender tail and small ears. The earliest 

 known species of Kangaroo, referred to before, M. bmni, belongs to 

 this section. Several examples were seen by Bruyn in 1711 living 

 in captivity in the garden of the Dutch governor of Batavia, and 

 described and figured in the account of his travels (Beizen <>rer 

 Moskome, etc.) under the name of "Filarider." It was quite lost 

 sight of, and its name even transferred by S. Miiller to another 

 species (Dorcopsis muelleri), until rediscovered in 1865 by Rosenberg, 

 who sent a series of specimens to the Leyden Museum from the 

 islands of Aru and Great Key, thus determining its true habitat. 

 M. thetidis is a well-known Australian representative of this 

 group. 



Extinct genera. In addition to the fossil forms already mentioned 

 which can be referred to existing genera, there are others from the 

 Australian Pleistocene indicating extinct generic types of Macropod- 

 idce, to which brief reference may now be made. The first of these 

 is Sthenurus, 1 represented by a single large species (S. atlas), and 

 characterised by the presence of a complete inner lobe to the fourth 

 upper premolar, and of an outer one in the opposing lower tooth, 

 so that these teeth present a flat and oval grinding surface when 

 worn. The median longitudinal bridge connecting the transverse 

 ridges of the molars is very imperfect ; and in the upper molars 

 there is no bridge between the first ridge and talon. In Procoptodon 2 

 the premolars resemble those of Sthenurus, but the molars are 

 elongated, and usually have their enamel thrown into numerous 

 vertical foldings. The most distinctive feature is, however, the 

 complete ankylosis of the mandibular symphysis ; the mandibular 

 rami being deep, and the diastema in the dental series short. The 

 lower incisors are nearly cylindrical, and the palate has large 

 vacuities. Three species are known. The largest representation of 

 the whole family is the type of the genus Palorchestes 3 (P. azael), in 

 which the length of the skull is estimated at sixteen inches. It is 

 distinguished from Procoptodon by the longer mandibular symphysis 

 and diastema, and the spatulate lower incisors. The true molars 

 have no distinct anterior talon, and are not grooved, while the 

 palate was fully ossified. 



1 Owen, Phil. Trans. 1874, p. 264. 

 2 Owen, op. cit. p. 788. 3 Owen, op. cit. p. 797. 



