CORAL POLTPiS. 



81 



times growing to a diameter of three feet. The common 

 large West Indian brain-coral is Mcsandrina labyrinthica. 



In Astrcea pallida Dana, of the Peejee Islands, the polyps 

 are pale, the disks bluish gray, and the tentacles whitish. 

 The polyps of many corals are beautifully colored. Those 



Fig. SS.—Zophokdia prolifera.— Alter WyvillK-Tkompsou. 



of Astrangia Dance Agassiz are white. In this coral, as 

 observed by Dana, the polyps stand prominently above the 

 calicles, as only their bases secrete coral. The tentacles 

 have minnte warty prominences, each full of lasso-cells. 



