CORALS AND CORAL MAKERS. 49 



Figure 4, in the same cut, represents a portion of a branch 

 of the Stylophora Dance E. and H. The corals of the genus 

 are remarkable for their small, crowded calicles, and for the 

 very distinct six-rayed star in each calicle (as shown magnified 

 in figure 5), and usually have a prominent point or columella 

 at the centre of the star. The polyp of a Feejee species, 6". 

 mordax, is represented in figure 6. The name of the family, 

 StylophoridcE (signifying style-bearer), alludes to this columella. 

 The corals grow in regular hemispherical clumps consisting of 

 flattened or rounded branches, and are sometimes a foot or 

 more across. 



In another family under this tribe, the FocilliporidcB^ very 

 common in coral-reef seas, the cells of the corallum are always 

 very small and crowded, as shown in figure 7. The corals 

 are branching, and in Pocillipora, the surface is often irregular 

 and warty, the little prominences, like the rest, being covered 

 with polyp cells ; while in Seriatopora, the branches are 

 slender, even, and pointed. The corallum in both is very firm 

 and soHd. In the larger part of them the number of tentacles 

 is only twelve, and formerly they were referred on this account 

 to the Madrepore tribe ; a few have as many as twenty-four 

 tentacles. 



The Pocilliporje form hemispherical clumps like the Stylo- 

 phorae ; and the branches vary from the flattened and broad 

 form shown in figure 7 (which represents the upper part of a 

 branch of the P.grandis D.), to irregularly cylindrical branches, 

 looking rough on account of the very short branchlets. The 

 cells are usually stellate, as in figure 8, from P. elongata D., 

 and often one of the septa, and sometimes two opposite ones, 

 extend to a columella at the centre, as illustrated in figure 9, 

 from P. plicata D. ; dividing the cell into halves. The cell in 

 the interior of the corallum is crossed by thin plates or tables, 

 as shown in figure 10, and hence they have been called tabulate 

 corals. Agassiz, after the discovery of the Hydroid character 

 of the animals of the Millepore corals, whose cells also are 

 tabulate, referred the Pocilliporae to the same Hydroid type. 

 But recent study of the polyps has shown that they are 



