MAMMALIA 453 



Order Insectivora (insect-feeders). — These are small mam- 

 mals with clawed digits, which feed on insects and other small 

 invertebrates. The brain is small and smooth. The incisors 

 are small. Many burrow, and have special adaptations for 

 such a life; among these one of the most interesting is the de- 

 generation of the eyes. The moles, shrews and hedgehogs are 

 the chief representatives. The moles have the reputation of 

 eating corn and other planted grains. Their burrows frequently 

 follow the rows. Their food, however, is the insects that collect 

 about the planted grain. They do. much damage to turf in 

 making their burrows. A single specimen has been known to 

 burrow twenty yards in a day. For brief periods and in reason- 

 ably firm soil they have been seen to dig a yard in ten minutes. 



Order Sirenia. — A small group of aquatic Placentalia, 

 more or less whale-like in form. They are sluggish, ungainly, 

 vegetable feeders. They have no posterior appendages and the 

 anterior are flipper-like, though capable of bending at the elbow. 

 They live near the shore and are represented by two living genera, 

 the sea-cow of our own eastern shores {Manatee), and the 

 Dugong of the Indian Ocean. 



Order Cetacea {Whales, Porpoises, Etc.). — The Cetacea are 

 aquatic mammals with a fish-like body. There are no posterior 

 appendages, and the anterior act as paddles, being without joint. 

 The tail is horizontally expanded into a powerful paddle, and a 

 dorsal fin is usually present. Teeth are present in the embryo, 

 but may be lost or replaced by "whale-bone" in the adult. 

 The stomach is chambered. The two' mammas are posterior. 

 Hair is very scant, but the layer of fat or "blubber" beneath 

 the skin is very thick, and serves as a non-conductor of heat. 



The whales are the largest living animals. The sulphur 

 bottom whale may reach a length of ninety-five feet and a 

 weight of 150 tons. It must be remembered that the whales 

 are air-breathers, and therefore must come to the surface to 

 breathe or "blow." The Cetacea prey on the smaller swim- 

 ming or floating animals found in the ocean, as fish, squid, 

 Crustacea, etc. Whales are principally sought for their fat and 

 baleen, or whale-bone. 



There are two principal suborders: the toothed whales, and 



