202 



PROF. P. MARTIN Duncan's reyision of the 



margin, and may pass from calice to calice. When there is continuity, the 

 costas are termed septo-costse. These may pass over the common wall and 

 base. 



Costae do not exist in some genera ; and, when they are developed, may 

 be spiuulose, moniliform, or smooth and lamellar. Some are crested and 

 spined. 



Endotheca or Dissepiments. Thin plate-like structures, oblique, arched, and 

 more or less distant, one above the other, in the interseptal loculi, and 

 sometimes, when there is no columella, in the axial space. They unite 

 septa, close the loculi, enable the coral to grow in height and strength, and 

 limit the growth downwards of the mesenteries and soft parts. 



Tahulce. Horizontal stout dissepiments, crossing much or all of the space 

 within the corallite-walls. 



Synajyticula. Special growths from the septal sides, reaching over the inter- 

 septal loculi to the other septa. They occlude much of the interseptal 

 loculi, often form a false basal wall to the corallite, and tend to form the 

 mural and basal structures in some genera. They are false when they only 

 consist of granular or papillary ornamentation united across the interspaces. 



Exotheca. A cellular structure stretching between neighbouring costse and 

 filling up the intercostal spaces, and often extending beyond the costse and 

 uniting neighbouring corallites When abundant, it forms a ccenenchyma. 

 It may be in bands, or may be very thick, and yet vesicular; in this last 

 instance it is termed perifheca. 



Epifheca. A basal structure covering all the outer structures of a colony or 

 corallura. It may reach close to the calice or only a little way from the 

 base. It may resemble the wall itself, or be membranous or pellicular, 

 and may be extended into radicles. It may be either smooth or transversely 

 wrinkled. 



Gemmation. This is rarely deciduous, and may arise from the calice — calicular 

 gemmation. If from between the axis and the calicular margin — intercali- 

 cular gemmation ; from the margin — marginal gemmation. Between calices 

 — intracalicular gemmation. It may occur from any part of the wall of a 

 corallite, from the calicular margin to the base — infra-marginal or lateral 

 gemmation. It may be close to or at the base — basal gemmation. Some- 

 times it occurs from stolons, or soft or solid growths from the base. 



Eissiparity. Union of septa across a calice and division of the corallite into two 

 or more parts, which become separate individuals, or by a continuance of 

 the process develop series. 



Collines or Ridges. The raised parts of a colony between series of calices, 

 usually covered by septo-costEe. 



Stereoplasm. A term usefully introduced by Lindstrom. Delicate endothecal 

 structure occupying different positions in the corallite, often forming ver- 

 tical processes in the interseptal loculi, or encircling septa, or acting as 

 true endotheca. Often filling up the base within, and then more solid. 



