ZOANTHAKIA. 



157 



over in silence. The major part of the species only occur in recent 

 geological strata. Nevertheless some of the species were very numerous 

 in the Cretaceous period, and even find representatives in the Silurian 

 period ; it is this group in which Madrepores of great size are found. 

 The family, as we have already said, take their names from their 

 supposed resemblance to the Mushroom. " But," says Peyssonnel, 

 " there is this difference between terrestrial and marine mushrooms 



Fig. 72. Fungia echinata (Milne Edwards). 



that the former have leaflets below, and those of the ocean have them 

 above (Fig. 72). These leaflets are only expansions of the Madre- 

 pores. Now, although I have not actually examined these petrified 

 Mushrooms of the sea, I have no reason to doubt but that they are 

 true genera or species of Madrepores, containing, like others, the 

 zoophytes which form them. In my travels in Egypt, in 1714 and 

 1715, I never heard it said that the Nile could produce them." In 

 this last remark, Peyssonnel makes allusion to the opinion .entertained 

 by many ancient authors, that the Fungia were productions of the Nile. 

 The animal is gelatinous or membranous, generally simple, de- 



