688 



MAMMALIA. 



length of the hind limb is due to the tibia and fibula, and to the foot. 

 The clavicles and fore arm are well developed. The epipubic or mar- 

 supial bones are large. 



The Kangaroos feed on herbage, and are often hunted down on 

 account of the damage which they do to pas- 

 tures and crops. The sharp incisors are suited 

 for cropping the grass and herbs, which the 

 ridged and tuberculated molars crush. 



As the Kangaroos are exclusively herbi- 

 vorous, it is not surprising to find that the 

 stomach is large and complex, with numerous 

 saccules on its walls. The whole gut is long, 

 and there is a well-developed caecum. 



Among extinct Marsupials there were some 

 gigantic forms, notably Diprotodon auslralis, 

 as large as a Rhinoceros. It is likely that 

 many of the early Mesozoic mammals were 

 Marsupials. The discovery of extinct Thy- 

 lacine-like marsupials in the lower Tertiaries 

 of Patagonia suggests an ancient land connec- 

 tion between Australia and the southern ex- 

 tremity of America. No other fossil Mar- 

 supials of Australian type are known in other 

 parts of the world. 



A remarkable new type of Marsupial (Noto- 

 ryctes typhlops) has been recently discovered 

 by Dr. E. C. Stirling. Four or five cervical 

 vertebrae are fused, there is a keeled sternum, 

 and a bird-like pelvis. The eyes are rudi- 

 mentary and beneath the skin. The marsupial 

 bones are small nodules. There is a functional 

 pouch. The animal is a rapid burrower. In 

 its mole-like characters it is a good illustration of " convergence," i.e., 

 the appearance of similar structures in forms not nearly related, appar- 

 ently in response to similar conditions of life. 



Most palaeontologists recognise, besides Marsupials and Monotremes, 

 another order of non-placental Mammals, the Multi-tuberculata, 

 wholly extinct. 



FIG. 248. Foot of 

 young Kangaroo. 



2-3, Small syndactylous 

 toes ; 4, large fourth toe ; 

 5, fifth toe. 



Sub-class EUTHERIA Order i. EDENTATA. 



This order includes five very distinct families with living 

 representatives the sloths, the ant eaters, the armadillos, 

 the pangolins, and the aard-varks. The first three families 

 are found in the New World, the last two in the Old World. 



Functional teeth are absent in several, but the ant eaters (Myrme- 

 cophagidse) are the only forms which still appear strictly edentulous. 

 When present the teeth are uniform, usually simple, without roots, 

 and with persistent pulp. They are never developed on the fore 



