38o 



CLASSIFICATION" OF VERTEBRATES. 



tn |, include the genera Perameles, in which the feet are much alike, and 

 Charopus, in which the hind legs are very long and the fourth toe alone 

 functional. The bandicoots {Peraineles) are no- 

 ticeable from the existence of a placenta. Fossils, 

 which in some respects closely resemble the polypro- 

 todonts and in some the insectivores, are the Tri- 

 CONODONTA and Tritiberculata, with the genera 

 AmphiUstes, (Jurassic, England and the U. S.), 

 Dicrocynodon (Jurassic, Wyoming), Arnphitherim 

 (English oolite). Dryolestes (Jurassic, Wyoming), 

 etc. 



Fig. 35S. Opossum, 

 Didelphys vir^iniana^ 

 after Audubon and 

 Bachman. 



Sub-Order 2. Diprotodoxta. 



1-3 



Incisors — -, the central ones larsre, the others 

 1-3 

 reduced ; canines small or absent ; molars with 

 blunt tubercles or transverse ridges. 

 In the kangaroos and wallabies (M.\cropodid.e) the hind legs are verv 



2 or I 4. 



I III - : 



10 o ' 2 or I 4 



very large. The larger kangaroos belong; to Macropus ; the arboreal tree- 



Icangaroos to Dendrolagus. Macropus, Palorchesies, etc., occur in .-Vustra- 



iian pleistocene. The Phalangistid.e includes climbing and flying 



•3 o I ' 



large; the feet as \n Perameles ; the teeth i -,c OT-,p' 



tail 



(soaring) forms, with legs of equal size, teeth / . , c _, 



i^^. Ill -. tail long. 

 2-1 4 " 



Tarsipes is an aberrant form about as large as a mouse. Petauriis, Be- 



lidius, etc., resemble the flying-squirrels in the lateral fold of skin and 



flying habits. Cusciis and Phalangista resemble the opossums in their 



prehensile tail. P/niSLolarctos. the koala, contains but a single climbing 



species two feet long. The Thylacoleonid.i: includes large fossil forms 



from the Australian pleistocene, with teeth 



■ P 



The kan- 



garoo-rats, or Hypsipry.mnid.e, with teeth i ^, c ^, p \ in f, resemble the 

 kangaroos in the disproportionate hind legs. Hypsiprvmnns. Bctttttt^ia, 

 the last also in the Australian pleistocene. The D1PROTODONTID.E in- 

 cludes only fossil forms of large size from the Australian pleistocene, with 

 the teeth / f , c ^, p \, in \. Diproiodon australis was larger than a rlii- 

 noceros ; the species of Xotothenutn somewhat smaller. The Phascolo- 

 3IYIDS, with a dental formula i\, c %, p\. tit i, diifer from all other mar- 

 supials in the presence of persistent dental pulps. The Tning wombats all 

 belong to Phascolomys, \\hich also occurs in the pleistocene. The e.xtinct 

 Phascaloims was as large as a tapir. South America has vielded se\eral 

 fossil diprotodonts of eocene or miocene age, and one recent species, 

 Ccsiioies/c-s obscurus, has been described from Colombia. 



