MADREPOEARIAN FAMILY THE rUNGIl>J3. 161 



septal loculus is filled up in its lower part, and up to a level with 

 the top of the smaller septa, by vertical or slightly curved solid 

 beam-like bodies with intervening canals, some of which open 

 through the base. 



This canal-system is most complete in Fungia and Herpolitha. 



The synapticula are grooved longitudinally, both axially and cir- 

 eum£erentially,.so as to enlarge the lumen of the canal; and this 

 gives the nipped-in appearance when they are seen from above. 

 They are very equal in size in the same corallum, exceptions to the 

 contrary relating to immature structures ; but large solid septa are 

 united to most delicate cribriform ones by as large synapticula as 

 are seen between well-developed septa. Again, thin fragile septa 

 unite with each other by dense synapticula as large as those found 

 between solid septa. 



The synapticula may be seen on the side of a large septum in 

 series, yet without a thin septum adhering to their flat free extre- 

 mity ; and hence the synapticulum may develop prior to one of 

 the septa to which it will eventually become attached. 



The extreme vertical height of the synapticula in Fungia in 

 the specimens examined was 12-14 millim. ; and they were as 

 stout as the walls of many corals, '5 millim. The spaces between 

 them, or canals, are narrower. 



In Halomitra the synapticula are long, vertical, and curved in 

 some parts, and are a succession of linear nodules in others ; and 

 it is to be noticed that whilst in Fungia the perforate condition 

 of the septa makes no difference in the continuity of the synap- 

 ticula, the fenestrate condition in Halomitra clearly relates to 

 their discontinuous nature. 



The sides of the septa of Fungidse examined are ornamented 

 with granules in rows and concentric series or in Vandykes. 

 This ornamentation differs in its direction from the synapticula, 

 and may be seen between them in some instances. 



Finally, the fibrous structure of the corals, made up of very 

 minute elongate prisms and fusiform bodies, is discontinuous here 

 and there between septa and synapticula ; and these last are 

 often formed independently of the septa. Frequently the synapti- 

 culum is a direct offshoot of two septa ; and the halves unite along 

 a line indicated by the presence of more connective tissue than 

 usual and by a difference in the direction of the ultimate fibres. 



