SUBDIVISIONS OF ACTINOID- POLYPS. 75 



dark blackish green or almost black color, while the polyps 

 have the tentacles nearly colorless, and the disk has a circle 

 of emerald green around the mouth. Dendrophyllia arbor ea is 

 the name of a common species of this genus found in deep 



POLYP OP DENDROPHYLLIA NIGRESCEN8. 



water in the Mediterranean ; it is equally large with the pre- 

 ceding, and somewhat similar in its mode of branching, but 

 a little stouter. It has also been found in the Atlantic about 

 the Azores. Another common Mediterranean species is 

 the D. coi'nigera. It is sparingly branched, and has very 

 long and stout corallets, sometimes as long and large as the 



O ' CD CD 



finger. 



The genus Gemmipora contains porous corals, of foliaceous, 

 bowl-like, and massive forms, covered by prominent cylindrical, 

 porous calicles, and having many short tentacles to the polyps, 

 usually in a single circle. 



Here belongs also the large Porites family (Poritidge), the 

 corals of which are very porous, and sometimes almost spongy, 

 and whose polyp-cells are exceedingly shallow, and usually only 

 imperfectly radiated. 



One of the genera in this family is Alveopora. It con- 

 tains the lightest of known corals, the texture being exceeding- 



