192 



THE OPAL SEA 



Holothu- 

 rians. 



Sen cu- 

 cumbers. 



Shell fieh. 



dernis they drop their feathery tentacles at 

 will and apparently without any lasting injury. 



The holothurians go beyond the star fishes 

 in the matter of dismemberment for they break 

 up into a dozen different pieces when occasion 

 requires. They have a body somewhat like the 

 sea worms, and might be put in the class with 

 them were it not for their spicules and tenta- 

 cles. There is no shell, but in its place a tough 

 leathery skin. A long bottle-shape has given 

 to one of the group the name of " sea cucum- 

 ber," and sometimes (but erroneously) " sea 

 slug." When seen in their habitat, say the 

 Florida coast, their colors are most attractive. 

 In China they are sought for food, and when 

 prepared for the trade make the well-known 

 " trepang." 



The molluscs come under the popular desig- 

 nation of " shell fish " and mean to the lay 

 mind primarily the oysters and clams of com- 

 merce; but the class is a large one and has 

 great variety. It embraces some twenty thou- 

 sand extinct species and as many more of the 

 living species. Every sea has its quota and 

 every shore has its shell-lined beach. The shell 

 is perhaps the most interesting part of the ani- 

 mal to the casual observer. It is usually made 

 of lime, is opaque; and within has a surface 



