176 



ANIMALS OF LAND AND SEA 



portion consists only of a relatively thin superficial layer. The 

 stony axis of the red coral is familiar to all because of its use 

 in jewelry. Some coelenterates reach a very large size, cer- 



FiGS. 521-532. Curious Crustaceans. 

 For explanations of the figures see pp. xxvii, xxviii. 



tain gorgonians attaining a height of 15 feet, and some sea- 

 pens being 6 or 7 feet or more in length. 



The colonial coelenterates consist of a great number of sac- 

 like units which have about the opening a row of 6 or 8 or 



