INTRODUCTION. 5 



The base, sides, calice, calicular edge or margin, are self-explaiiative terms. The 

 terms calicular fossa, and interseptal loculi, have been noticed. 



These are the usual structures observed, and they are modified in every way to 

 produce the various shapes of corals. 



The word corallum is used to individual corals when solitary in their growth ; but 

 when aggregated to form a compound mass each individual of the mass is called a 

 corallite, the aggregation retaining the name of corallum. 



The corallites of a compound corallum may be united together by the fusion of their 

 walls, no costae existing, or they may be united by a great development of the costae and 

 the exothecal dissepiments. Sometimes the exotheca is so developed as to form a very 

 distinct tissue between the corallites ; it is then more or less cellular, and is termed 

 cmnencliyma anA peritheca. 



Some simple and many compound corals extend by a process of lateral calicular 

 growth, so that there is not a circular or ovoid calice, but a long, and often gyrate assem- 

 blage of septa ; such a calice is called " serial." The shape of compound corals is deter- 

 mined, to a great extent, by their method of gemmation} and by the existence of 

 Jissiparotis " and serial^ calices. 



II. — Anatomy of the Sclerenchymatous Structures. 



Calice, Wall, Septa, Pali, Columella, Costce, Endotheca, Exotheca, Epitheca, Feritheca, 



Ccenenchyma. 



Calice. — The upper and open extremity of a coralluui is called its calice.^ Its outline 

 is formed by the upper or marginal part of the luall, and is very various in its form. The 

 superior boundary is determined by the greater or less exsertness of the septa, and its 

 depth by the greater or less prominence of the structures forming the floor of the 

 fossa. 



The periphery of the calice is called its margin, and its floor is formed by the septa, 

 the interloculi, the top of the columella, and, when that structure does not exist, by the 

 axial space. 



Every variety of form may be noticed in the outlines of calices ; they may be circular, 

 circular and slightly compressed, oval, elliptical, elliptical and slightly angular at the end 

 of the long axis, ovoid and compressed from side to side, ovoid at one end, linear or leaf- 



1 Plate III, fig. 15 ; Plate IV, figs. 10, 11, 17, 18. 



2 Plate IV, figs. 12, 13. 3 Plate IV, figs. 14, 15. 



* Plate I, figs. 1, 11, 6 ; Plate II, figs. 11, 13, 14 ; Plate III, figs. 15, 17, 18, 19, 20 ; Plate IV. figs. 

 8, 11, 12. 



