64 CORALS AND CORAL ISLANDS. 
2. Polyps having internal calcareous secretions. MApDREPO- 
RARIA Of VERRILL (the Cyathophylloid species excluded). 
HEXACORALLA of some authors. 
4. Astrea tribe, or ASrraacEa.—In this tribe the polyp- 
cells or calicles are distinctly lamello-radiate within, and gen- 
erally so outside. Moreover, budding is always by division 
of the disks, or spontaneous fission. The figure of the Cau- 
lastreea, on page 58, illustrates one section of this family, that 
in which each branch of the corallum is made by a single 
polyp, and branching is by furcation through spontaneous fis- 
sion. In other related genera, as Mussa, the polyps sometimes 
have a diameter of two inclies, being as large as ordinary 
Actinie. 

ASTRA PALLIDA, D. 
The Ast7@a pallida is a good representative of the massive 
Astreas. The color of the polyps in this species is quite pale, 
the disks being bluish-gray, and the tentacles whitish. In oth- 
ers, the tentacles are emerald-green, or deep purple, or of other 
shades. 
