INTRODUCTION. O 



by the D. ursinus, are now extinct on the Australian continent ; 

 but one species of each still exists on the adjacent island of 

 Tasmania; the rest were extinct Wombats, Phalangers, Potoroos, 

 and Kangaroos — some of the latter [Macrojms Atlas, M. Titan) 

 being of great stature. A single tooth, in the same collection 

 of fossils, gave the first indication of the former existence of a 

 type of the Marsupial group, which represented the Pachyderms 

 of the larger continents, and which seems now to have disappeared 

 from the face of the Australian earth, — of the great quadrui)ed, 

 so indicated under the name oi Diprotodon'wx 1838; and suc- 

 cessive subsequent acquisitions have established the true mar- 

 supial character and the near affinities of the genus to the Kan- 

 garoo {Macrojms), but with an osculant relationship with the 

 herbivorous Wombat. The entire skull of the Diprotodon, lately 

 acquired by the British Museum, shows in situ the tooth on 

 which the genus was founded. This skull measures 3 feet in 

 length, and exemplifies by its size the huge dimensions of the 

 j)rimeval Kangaroo. Like the contemporary gigantic Sloth in 

 South America, the Diprotodon of Australia, while retaining the 

 dental formula of its living homologue, shows great and remark- 

 able modifications of its limbs. The hind ])air were much 

 shortened and strengthened compared with those of the Kan- 

 garoo ; the fore pair were lengthened, as well as strengthened. 

 Yet, as in the case of the Megatherium, the ulna and radius 

 were maintained free, and so articulated as to give the fore paw 

 the rotatory actions. These, in Diprotodon, would be needed, as 

 in the herbivorous Kangaroo, by the economy of the marsupial 

 pouch. The dental formula of Diprotodon was the same as in 

 Macropus major: the first of the grinding series was soon shed, 

 but the other four two-ridged teeth were longer retained ; and 

 the front upper incisor was very large and sealpriform, as in the 

 Wombat. The zygomatic arch sent down a process for augment- 

 ing the origin of the masseter muscle, as in the Kangaroo. The 

 foregoing skidl, with parts of the skeleton of the Diprotodon 

 amlralis, were discovered in a lacustrine deposit, probably 



