CCELENTERATA. 



253 



FIG. 201. Madrepora aspera, living and expanded ; natural size. Pacific. 



whose mean temperature in the coldest month is below 

 68 Fahr., nor at greater depth than twenty fathoms. The 

 most luxuriant reefs are in the Central and Western Pa- 

 cific and around the West Indies. 



FIG. 202. Ctenactis echinata, or " Mushroom-coral ;" one fourth natural size. Pacific. 



