CHAPTER VII 



EUTHEKIA .MAIiSUPIALIA 



Order I. MARSUPIALIA ^ 



The Marsupials may be thus defined : — Terrestrial, arboreal, or 

 burrowing (rarely aquatic) mammals, with furry integuments ; 

 palate generally somewhat imperfectly ossified ; jugal bone reach- 

 ing as far as the glenoid cavity ; angle of lower jaw nearly always 

 inflected. The clavicle is developed. Arising from the pubes are 

 well developed and ossified epipubic bones. Fourth toe usually 

 the most pronounced. Teeth often exceed the typical Eutherian 

 number of forty-four ; molars generally four on each side of each 

 jaw. As a rule but one tooth of the milk set is functional, which 

 is (according to many) the fourth premolar. Teats lying within 

 a pouch, in wliich the young are placed. Young born in an im- 

 perfect condition, and showing certain larval characters. There 

 is a shallow cloaca. The testes are extra-abdominal, but hang in 

 front of the penis. In the brain the cerebellum is completely 

 exposed ; the hemispheres are furrowed, but the corpus callosum 

 is rudimentary. An allantoic placenta is rarely present. 



Structurally the Marsupials are somewhat intermediate be- 

 tween the Prototheria and the more typical Eutheria, with a 

 greater resemblance to the latter. 



The name Marsupial indicates what is perhaps the most 

 salient character of this order. The pouch in which the young 

 are carried is almost universally present. It is less developed 



1 Works dealing exclusively with the Marsupials are : Lydekker, in Allen's 

 KatLbralists' Library, 1894 ; Aflalo, Natural History of Australia, Macmillan and 

 Co. 1896 ; Waterhouse, Natural History of Mammalia, i. London, 1848 ; Old- 

 field Thomas, British Museuvi Catalogue of Marsupialia wad Monotremata, 1888. 



