70 CORALS AND CORAL ISLANDS. 
as to go by the popular name of ‘‘ white coral,” and to be some- 
times polished for beads and other such ornamental purposes. 
Figure 2 is a branch of a beautiful little coral called Sty- 
laster erubescens Pourt., and 3, a portion of the same enlarged. 
It has the firmness, and something of the habit of an Oculina, 
but is rather like a miniature Oculina, its calicles never exceed- 
ing a twentieth of an inch in breadth. The Stylasteride 
have been shown, however, to be Hydrocorailine, like the 
Millepores (page 103). 
Figure 4, in the same cut, represents a portion of a branch of 
the Stylophora Danw KE. und 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, S. 
mordax, is represented in figure 6. The name of the family, 
tylophoride (signifying style-bearer), alludes to this colu- 
mella. The corals grow in regular hemispherical clumps con- 
sisting of flattened or rounded branches, and are sometimes a 
foot or more across. 
In another family under this tribe, the Pociliporide, 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 1s 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 sol- 
id. 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 tenta- 
cles. 
The Pocilliporze form hemispherical clumps like the Stylo- 

