520 Verrill, Notes on Radiata. 



round, and obtuse, or very broad and convoluted lobes or fronds, 

 which arise from a more or less compact encrusting base. Branches 

 often covered with verrucse or rudimentary branchlets, composed of a 

 few or many cells. At the ends of the branches the cells are closely 

 crowded, angular, closely united by their walls, without intervening 

 coenenchyma, but on the sides of the branches they are more or less 

 distantly separated by the compact coenenchyma, which is sharply 

 granulous or spinulose at the surface. Cells small, often deep, circular 

 where not crowded, often filled below the surface by a solid deposit, 

 but always with transverse septa in the lower parts, which are abun- 

 dant and regulai'. Septa narrow, generally 12, of which 6 are larger 

 and alternate with six that are very small or rudimentary ; sometimes 

 24. The septa are often partially or wholly rudimentary or abortive, 

 especially in the crowded cells at the end of the branches, but in many 

 cases two opposite ones are larger than the rest and join the colu- 

 mella, or there may be one larger one. The columella, when present, 

 is small, solid, a little prominent, but is often wanting. The trans- 

 verse plates have a concentric structure and are often seen incomplete, 

 with an opening through the middle. Occasionally a cell is divided 

 by fissiparity, but the new ones mostly appear in the angles between 

 adjacent cells. 



This genus is very abundant throughout the tropical parts of the 

 Pacific and Indian Oceans and the Red Sea. At the Hawaiian Islands 

 several large species of Pocillipora constitute an important part of 

 the coral-reefs. In the Atlantic ocean the genus is unknown, but a 

 fossil species occurs in the Miocene of the West Indies. 



Pocillipora capitata Veniii. 



Pocillipora capitata Verrill, Bulletin Mus. Comp. ZooL, p. 60, 1864; Proc. Essex 

 Inst., vi, p. 99, 1869. 



Coralla composed of clusters of large, irregular, usually stout 

 branches, often an inch or more in diameter, arising from a massive 

 or encrusting base. The branches are covered, except at the ends, 

 with more or less elongated, rising, subacute or bluntly rounded 

 verrucse. The branchlets are usually spreading, often rounded or 

 clavate at the end, where the verrucse become obsolete. Suiface 

 covered with small, rough, scattered spinules, those around the edge 

 of the cells more prominent. Cells rather small, circular and deep 

 on the side of the branches, and mostly separated by spaces at least as 

 broad as the diameter of the cells, sometimes more crowded ; on the 

 ends of the branches and verrucse, the cells are angular and separated 



