494 



MAMMALS. PHYLUM CHORDATA 



the Forestry Commission. It is by nature an animal of the woods, 

 and it is onlv necessity that has driven it to the hills of the west 

 and north. The roe has also expanded its range and is now found 

 in woodlands in various parts of England. The fallow deer 



Fig. 386.— a side view of a sheep's skull, with the roots of the back teeth exposed. 



— From Thomson. 



/.. Frontal ; n., nasal ; pm., premaxilla ; m., maxilla ; ;., jugal ; sq., squamosal ; /., lacrimal. 



(Dama dama), introduced centuries ago and commonly kept in 

 parks, has also benefitted by the planting of the past thirty 

 years, and is now more widely spread, as a truly wild animal, 

 than either of the other two species. A few other introduced 

 species of deer have also become wild in some woods. 



MARSUPIALIA 



Besides the Eutherian mammals which suckle their young 

 there are two other subclasses in existence in the world to-day. 

 The more advanced of these are the Metatheria or Marsupiaha. 

 The most striking feature is that the young, though born alive, 

 is very small and climbs tropistically to the nipple and there 

 becomes attached for a long time. The mammary glands are 

 situated in an abdominal pouch or marsupium, supported by 

 bones attached to the pubes, and milk is pumped into the baby, 

 which has a forward prolongation of the larynx into the nasal 

 passage ( a true larval character, p. 345) so that it shall not choke. 

 There is no true placenta. Apart from the method of care for the 

 young, which is rather specialised, the marsupials have remained 

 somewhat primitive. Their skull (Fig. 387) has many of the 

 features found in insectivores, such as the fenestrated palate 

 and the absence of a tympanic bulla, but can be distinguished 

 by the fact that the angle of the lower jaw is turned inwards 



