436 



CHAPTEE XIX. 



M A M M A L I A— Continued. 



CLASSIFICATION OF MAMMALS. 



BRITISH MAMMALS (DOMESTIC AND WILD). 



Mammalia are divided into three sub-classes — namely, the 

 Ornithodelphia, the Didelphia, and the Monodelphia^ — which 

 are characterised by the following features : — 



A. The Ornithodelphia have the two uterine enlargements 

 of the oviducts separate, forming two uteri, each of which opens 

 direct into a cloacal chamber like a bird, and not into a single 

 vagina. This cloaca also receives the rectum and ureters. 

 Chorion absent. Here are placed the Monotr&mata, to which 

 belong the Echidna and Duck-Bill {Ornithorhynchus). 



B. The Didelphia, characterised by the uterine enlargements 



1 Huxley, in the ' Proceedings ' of the Zool. Soo. for 1880, p. 649, pro- 

 posed the following names for these three groups : (1) Prototheria, (2) 

 Metatheria, (3) Eutheria. Dr Gadow, in his new classification of the Verte- 

 brata, follows Huxley's three divisions, and groups the Mammals in the 

 following order : — 



Sub-class 1. Prototheria (Monotremata, &o.) 



Sub-class 2. Metatheria (Marsupials). 



Sub-class 3. Eutheria. 

 Order 1, Edentata. Order 2, Trogontia (including the Rodentia). 

 Order 3, Cetacea. Order 4, Sirenia. Order 5, Ungulata (including 

 Hyracoidea and Proboscidea). Order 6, Carnivora. Order 7, Insectivora. 

 Order 8, Chiroptera. Order 9, Primates. 



