CHAPTER XX 



MAMMALS. GENERAL PRINCIPLES OF THEIR DISGUISING-COLORATION. FULL 

 OBLITERATIVE SHADING ALMOST UNIVERSAL AMONG THEM. EXCEPTIONS 

 CONSIDERED 



ALMOST all mammals, from some of the biggest oceanic cetaceans to 

 -^ *■ the smallest terrestrial quadrupeds, are equipped with a full obliterative 

 shading of surface-colors. That is, they are darkest on the back and lightest 

 on the belly, usually with connecting intermediate shades. White is by far 

 the commonest color for the middles of their undersides, while the dark of 

 the upper sides very often culminates in a black or dusky median line, a sort 

 of painted 'ridge pole,' laid along the center of the back, over the tips of the 

 dorsal vertebrae. With or without such extreme accentuation, complete ob- 

 literative shading characterizes most of the species of almost all the mam- 

 malian orders. This generalization applies to the great order Marsupialia, 

 comprising the kangaroos, opossums, phalangers, the Tasmanian wolf, and 

 many other forms; to the marine order Cetacea (whales, dolphins, porpoises, 

 etc.); to the order Chiroptera, or bats; to the vast order Rodentia, including 

 rats, mice, squirrels, beavfers, hares, agoutis, porcupines, etc.; to the order 

 Insectivora (hedgehogs, shrews, moles, etc.); to the order Ungulata (hoofed 

 animals, among which we may here include, for convenience, the elephants 

 and the hyrax, as well as the tapirs, rhinoceroses, and the hippopotami) ; to 

 the great order Camivora (containing the cats, from the lion to the lynx, the 

 civets, mongooses, and hyenas; the canine beasts — dogs, wolves, jackals, 

 foxes, etc.; the otters, weasels, raccoons, badgers, bears; the sea lions, wal- 

 ruses and seals) ; and to the order Primates., including lemurs, monkeys, apes 

 and man. But in all the above-named orders, and notably in Ungulata, Chir- 

 optera, and Primates, there are exceptions to the rule. These exceptions are 



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