46 



CORALS 



OCULIXA. — The genus Oculina belonging to this family 

 is found in a few fathoms of water in the warmer tropical 

 seas. Like the other genera that have been described, the 

 corallum is sparsely branched, and sometimes shows anasto- 

 moses and fusions of the 

 branches. 



The coenosteum is very 

 hard and solid. The calices 

 are relatively more numer- 

 ous and very shallow, and 

 are usually arranged in 

 steep spiral rows on the 

 branches. The rims of the 

 calices project a little from 

 the surface, giving it a 

 warty or verrucose appear- 

 ance. The number of septa 

 varies, but is usually about 

 twenty-four, and standing 

 opposite the free edges of 

 the principal orders of the 

 septa there are pali. The 

 columella is variable, but 

 frequently consists of a few 

 short pillars very similar 

 in appearance to the pali. 



Family 3. Astraeidae 



The familv of the As- 

 Fig. i4.-Ocuiina. A small piece of a tracidac or Star-corals is, 



branch of a large colony. Nat. size. _ _ 



in respect of variety of 

 structure and number of generic forms, the largest and most 

 difficult of all the families of the Madreporaria. 



The family pla\'ed an important part in building up the 

 coral reefs of the Jurassic, Cretaceous, and early Tertiary 

 times, but in later Tertiary and in recent times, although 

 still very abundant in some localities, they take a second 

 place in reef-building powers to the more vigorous and 



