THE VERTEBRATES: MAMMALS 249 



roptera, differ from all other mammals in having the fore 

 limbs modified for flight by the elongation of the forearms 

 and especially of four of the fingers, all of which are con- 

 nected by a thin leathery membrane which includes also 

 the hind feet and usually the tail. Bats are chiefly noc- 

 turnal, hanging head downward by their hind claws in 

 caves, hollow trees, or dark rooms through the day. They 

 feed chiefly on insects, although some foreign kinds live 

 on fruits. There are a dozen or more species of bats in 

 North America, the most abundant kinds in the Eastern 

 States being the little brown bat {Myotis subulatus), about 

 three inches long with small fox-like face, high slender 

 ears, and a uniform dull olive-brown color; and the red 

 bat {Lasiurus borealis), nearly four inches long, covered 

 with long, silky, reddish-brown fur, mostly white at tips 

 of the hairs. 



The dolphins, porpoises, and whales (Cete). — The 

 dolphins, porpoises, and whales (Cete) compose an order 

 of more or less fish-like aquatic mammals, among which 

 are the largest of living animals. In all the posterior limbs 

 are wanting, and the fore limbs are developed as broad 

 flattened paddles without distinct fingers or nails. The 

 tail ends in a broad horizontal fin or paddle. The Cete 

 are all predaceous, fish, pelagic crustaceans, and especially 

 squids and cuttlefishes forming their principal food. Most 

 of the species are gregarious, the individuals swimming 

 together in "schools." The dolphins and porpoises com- 

 pose a family (Delphinidse) including the smaller and many 

 of the most active and voracious of the Cete. The whales 

 compose two families, the sperm-whales (Physeteridee) with 

 numerous teeth (in the lower jaw only) and the whalebone 

 whales (Baleenidae) without teeth, their place being taken 

 in the upper jaw by an array of parallel plates with fringed 

 edges known as "whalebone." The great sperm-whales 

 or cachalots (Physeter macrocephalus) found in southern 



