MADREPORARIAN CORALS 37 



of these corals, which are essential for the understanding 

 of the classification, we may now proceed to the study of 

 the families. 



Family i. Tureinoliidae 



The corals included in this family are mostly solitary 

 in habit, and are either attached to rocks, shells, and other 

 foreign objects, or in some cases rest freely in or on a sandy 

 sea-bottom. 



They may be distinguished from the solitary corals 

 belonging to the other families by being imperforate and by 

 having septa which liave usually smooth surfaces ; but if 

 the septa are armed with spines or tubercles, they are not 

 joined together bv bars (Synapticula) of coral substance as 

 they are in the Fungiidae. 



From the solitary and imperforate corals of the family 

 Astraeidae, the Turbinoliidae are distinguished by the 

 occurrence in the former of dissepiments or tabulae which 

 shut off the living polyp below from the original base of 

 the calyx, whereas in the latter the spaces between the 

 septa pass right down to the base of the calyx. 



The British cup-coral CaryopJiyllia smithii has been 

 described on p. 26. It is found at low tide attached to 

 the rocks near Ilfracombe, on the breakwater at Plymouth, 

 and probably in other localities on the coast of Cornwall 

 and Devon. It is also found at Roscoff on the coast of 

 Brittany and on the coast of Norway. Other species of 

 the genus Caryophyllia occur in the Mediterranean Sea, 

 and the genus seems to have a pretty wide distribution in 

 shallow water. 



The only other corals belonging to this family that have 

 been found on the British coast belong to the genera Para- 

 cyathus and Sphenotrochus They occur only in deep 

 water off the Atlantic coasts and may be regarded as 

 among the rarities of our marine fauna. 



The genus Paracyathus, however, seems to be very 

 abundant in some other localities, and requires a few words 

 of description. 



Paracyathus. — A large number of specimens of Para- 



