MAMMALS 



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their own ; ^ and they nurse their young with milk secreted by glands known as 

 the mammary glands; hence the term "mammal." 



Of the 3500 species, most inhabit continents ; a few species are found on 



inhabit the ocean. They vary in size from 

 tiny shrew mice and moles. Adaptations 



Sea lion, a mammal adapted to life in the sea. 



islands, and some, as the whale, 

 the whale and the elephant to 

 abound: the seal, the sea lion, 

 and the whale have limbs modi- 

 fied into flippers ; the sloth and 

 squirrel have limbs peculiarly 

 adapted to climbing ; while the 

 bats have the fore limbs modi- 

 fied for flight. 



The lowest mammals are the 

 monotremes. Although they are 

 provided with hairy covering 

 like other mammals, they lay 

 eggs like the birds. Such are 

 the Australian spiny anteater 

 and the duck mole. 



All other mammals bring forth their young alive. The kangaroo and opos- 

 sum, however, are provided with a pouch on the under side of the body, in 

 which the very immature, blind, and helpless young are nourished until they are 

 able to care for themselves. These pouched animals are called marsupials. 



The other mammals may be briefly classified as f ollov/s : — 



Classification of Highee Mammals 



Order 1. Edenta'ta. Toothless or with very simple teeth. Examples: anteater, sloth, 

 armadillo. 



Order 2. Ceta'cea. Adapted to marine life. Examples: whale, porpoise. 



Orders. Sire'nia. Fishlike in form; pectoral limbs paddle-like. Examples: manatee, dugong. 



Order 4. Roden'tia. Incisor teeth chisel-shaped, usually two above and two below. Ex- 

 amples: beaver, rat, porcupine, rabbit, squirrel. 



Order 5. Ungula'ta. Hoofs ; teeth adapted for grinding. Examples : (a) odd-toed : horse, 

 rhinoceros, tapir ; (6) even-toed : ox, pig, sheep, deer. 



Order 6. Insectiv'ora. Small, insect-eating, furry or spiny covered ; long snout. Example : 

 mole. 



Order 7. Carniv'ora. Long canine teeth, sharp and long claws. Examples: dog, cat, lion, 

 bear, seal, and sea lion. 



Order 8. Cheirop'tera. Fore limbs adapted to flight, teeth pointed. Example : bat. 



Order 9. Prima'tes. Erect or nearly so, fore appendage provided with hand. Examples : 

 monkey, ape. Anatomically, man is placed with this highest group of mammals. 



Increasing Complexity of Structure and of Habits in Plants and 

 Animals. — In our study of biology so far we have tried to get 

 some notion of the various factors which act upon living things. 

 We have seen how plants and animals interact upon each other. 



1 All except the monotremes. 



