432 



ZOOLOGY 



SECT. 



Striges, the Picarise, and especially the Passeres. Among the latter 

 the Corvidse (Crows) are probably to be looked upon as the most 

 exalted members of the class (Fig. 1090). 



PASSERES 



GAVIAE 

 COIYMBI \ICHTHVORNITHES 



N! 



ODONTOLCA 



GALLINAE 



CRYPTURI 



MEGISTANES 



ORNITHOSAURIA 



DINOSAURIA 



FIG. 1090. Diagram illustrating the Relationships of the chief groups of Birds. 



CLASS VI. -MAMMALIA. 



The class Mammalia, the highest of the Vertebrata, comprises 

 the Monotremes and Marsupials, the Hoofed and Clawed Quadrupeds, 

 the Whales and Porpoises and Sea-Cows, the Rodents, Bats and 

 Insectivores, the Lemurs and Apes, and the Human Species. All 

 Mammals, though many are aquatic, are air-breathers throughout 

 life, lungs being, as in Reptiles and Birds, the sole organs of respira- 

 tion. The blood of Mammals has a high temperature, resembling 

 in that respect the blood of Birds and differing from that of Reptiles 

 and Amphibia. The scales of Reptiles and the feathers of Birds 

 are replaced in Mammals by peculiar epidermal structures, the 

 hairs, usually developed in such quantities as to form a thick, soft 

 covering or fur. The young are nourished after birth by the secre- 

 tion of mammary or milk-glands. 



1. EXAMPLE OF THE CLASS THE RABBIT (Lepus cuniculus). 



External Characters. The Rabbit (Fig. 1091) is a four- 

 footed or quadrupedal animal, having the whole surface of its 

 body covered with soft fur. The head bears below its anterior 



