64 CORALS AND CORAL ISLANDS. 



2. Polyps having internal calcareous secretions. Madeepo- 

 eaeia of Veeeill. ( The Cyathophylloid species ex- 

 cluded. ) 



4. Astrwa tribe, or Aste^eacea. — 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- 

 lastraea, 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 inches, being as large as ordinary 

 Actinia?. 



ASTR*EA PALLIDA, D. 



The Astrwa pallida is a good representative of the massive 

 /Astrseas. 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. 



