MADREPORARIAN CORALS 63 



imperforate, there are some forms in which either septa or 

 theca or both are porous. It is quite clear that any attempt 

 to divide this family into two groups on the character of the 

 perforation or imperforation of the corallum would be un- 

 natural and unsound. 



The genus Fungia (Fig. 2^) is a solitary coral and can 

 readily be distinguished from the solitary corals of other 

 families of Madreporaria, but nearly ah the other genera are 

 compound or colonial corals, the corallum being built up by 

 the activities of a large number of polyps, and many of these 

 seem to approach very closely in structure to corals belonging 

 to other families. It is in such cases that the determination 

 of the presence or absence of synapticula becomes a matter 

 of great importance. 



According to the system adopted by Duncan and sub- 

 sequent authors, the group of corals which is here called 

 Fungiidae constitutes a separate section of the Madreporaria 

 called the Madreporaria fungida, and this section is divided 

 into a number of families. Of these families the one called 

 Fungiidae includes the genera Fungia, Halomitra, Herpeto- 

 litha, etc., the family Plesiofungiidae includes the important 

 genus Siderastraea, and the Lophoseridae includes the genera 

 Agaricia, Pach^-seris, Pavona, etc. The Plesiofungiidae are 

 in some respects a transition group between the Fungiidae 

 and the Astraeidae, and an extinct family, Plesioporitidae, 

 forms a transition group between the Fungiidae and the 

 Madreporidae. 



Fungia. — The best known and most widely distributed 

 of the genera of the Fungiidae is the " Mushroom coral," 

 Fungia. On many of the tropical coral reefs of the old 

 world it can be collected in cart-loads, and attracts attention 

 not only on account of its size — for it may be a foot in 

 diameter — but on account ot its curious resemblance to the 

 inverted disc of a mushroom. Moreover, it differs from the 

 other corals of the reef in being free, in the adult condition, 

 so that it can be lifted and examined without forcibly 

 detaching it from any basal support. 



The history of our knowledge of Fungia presents^^me 

 features of special interest to which reference rm 



