THE DISTRIBUTION OF ANIMALS 467 



Another interesting game bird, the heath hen, which was formerly 

 common in the eastern states, had by 1921 been reduced to a small flock 

 on Martha's Vineyard Island off the coast of Massachusetts. About 

 that time a disastrous fire swept the island during the nesting season 

 and is believed to have destroyed both the nests and the female birds 

 that were incubating. All but one or two females and about a dozen 

 males were killed. These survivors lived for a time on the island but 

 all died without further reproduction. 



The extinction of the dodo bird is another example of man's thought- 

 lessness in exterminating valuable animals. The dodo was a flightless 

 bird belonging to the pigeon order which lived on the Island of Mauritius 

 in the Indian Ocean. This large, heavy-bodied bird was so clumsy that 

 the sailors killed it with clubs. Pigs, dogs, and other imported ani- 

 mals finished the extermination, and none were reported after 1681. 

 We have the common expression "dead as a dodo" to remember them by. 

 A few skeletons were dug up two hundred years later in a swamp on the 

 island and mounted. 



In 1741 a Russian whaler put in at one of the Aleutian Islands and a 

 man named Stellar found a large group of seacows there. They were 

 called Stellar's seacows. Within twenty-five years, however, the pass- 

 ing whalers had killed the last of these animals, and they have never 

 been seen since. 



Several species of river snails became extinct when the Norris Dam 

 was built and flooded the Clench River. These snails had a very re- 

 stricted range in the rapids of the river and could not survive in the 

 calm waters of the lake. 



Discontinuous Range 



A number of species or groups of related species of animals have a 

 peculiar distribution on the face of the earth which is difficult to ex- 

 plain without a knowledge of the geological record. The tapir is a hog- 

 like animal found in Central America, South America, and Sumatra. 

 The alligator is found only in central China and the southeastern part 

 of North America. A lizard known as the skink is found in Southeast- 

 ern United States, China, and Japan. The horseshoe crab occurs on 

 the Atlantic Coast of North America and on the coast of the Molucca 

 Islands in the East Indies. Marsupials are found in the Australian 

 region and a few in the Americas, but not in between. 



Related genera may also be interesting in their distribution. There 

 are three known lungfish in the world ; they are found in tropical South 

 America, Africa, and Australia— as far apart as a world of this size will 



