62 



THE ANTHOZOA 



58, 59, 63) ; von Heider (38) ; Fowler (23-26) ; Bourne (6 and 7) ; 

 and Ogilvie (103). 



The relations of the zooid to the skeleton may be studied in 

 Fig. XXVIIL, which represents a diagrammatic longitudinal section 

 through a Turbinolid coral. A quadrant is cut out on the left 

 side to further display the anatomy. In the skeleton of a typical 

 solitary coral the common Devonshire cup -coral, Caryophyllia 

 Smithii, is a good example the following parts are to be dis- 



Th. 



FIG. XXVIIL 



Diagram illustrating the relation of the soft tissues to the corallum in a solitary aporose 

 coral. St, stomodaeuin ; Sul, sulcus ; M, mesenteries ; Th, theca ; S, septa ; Col, columella ; Ep, 

 epitheca ; P, edge-zone. 



tinguished : (1) The basal plate, between the zooid and the 

 surface of attachment. (2) The septa, radial calcareous laminae 

 reaching from the periphery to near or quite to the centre of the 

 calycle. (3) The theca or wall, which, in many corals, is not an 

 independent structure, but is formed by the conjoined peripheral 

 ends of the septa. (4) The columella, a structure which occupies 

 the axis of the corallite, and may be solid or trabeculate. If it 

 arises from the base, it is termed essential ; if formed by the 

 union of trabeculae from the septa, it is termed unessential. (5) 

 The costae, longitudinal ribs or rows of spines on the outer surface 

 of the theca. True costae always correspond to the septa, and 

 are in fact the peripheral ends of the latter. (6) Epitheca, an 

 offset of the basal plate which surrounds the base of the theca in 

 a ring-like manner. (7) Pali, laminae which extend upwards from 



