THE ECHINODERMS 



197 



It is then forcibly drawn out through the closed lips so that all 

 the living cargo is swept off." 



Among the South Pacific islands sea cucumbers are known 

 as " beche de mer " or " trepang " and are used for food. The 

 trade mounts into hundreds of thousands of dollars annually. 



Fig. 117. — A sea cucumber. (From Clark.) 



Sea Lilies. — The sea lilies or crinoids are now less abun- 

 dant than the other echinoderms, but were very numerous in 

 bygone eras, as indicated by their fossil remains so often found 

 in limestone. They live usually at moderate depths and are 

 therefore not seen so frequently along the coast. 



REFERENCES 



Cambridge Natural History, Vol. I. — The Macmillan Co., N. Y. City. 

 College Zoology, by R. W. Hegner. — The Macmillan Co., N. Y. City. 

 The Sea Beach at Ebb Tide, by A. F. Arnold. — The Century Co., N. Y. 

 City. 



