ANTHOZOA. ZOANTHARIA 93 



theca with folds. Trias to Cretaceous ; in England, Inferior Oolite 

 to Corallian. Ex. S. tubulifera, Corallian. 



Thecosmilia. Compound, dendroid or rarely almost massive. 

 Multiplication by fission. Margins of calyces irregular. Columella 

 rudimentary or absent. Septa strong, upper edges dentate, more or 

 less exsert. Dissepiments abundant. Epitheca thick and folded, 

 but often not preserved. Trias to Tertiary ; in England, Lias to 

 Kimeridgian. Ex. T. annularis, Corallian and Kimeridgian. 



Holocystis. Compound, massive, convex ; calyces polygonal. 

 Columella very small or absent. Corallites united by their walls or 

 by costse. The four principal septa are much better developed than 

 the others. Tabulse well developed. Lower Greensand. Ex. H. 

 elegans. 



3. Perforate Corals. 



Thamnastraea. Compound, massive ; convex or laminar. 

 Walls of the corallites indistinct. Calyces shallow. Septa formed 

 of fan-shaped rows of rods ; the septa of adjoining corallites con- 

 fluent ; faces of septa with granulations. Columella small, trabe- 

 culate. Dissepiments present, synapticulse numerous. Usually a 

 basal epitheca. Trias to Miocene ; in England, Lias to Upper 

 Greensand. Ex. T. arachnoides, Corallian. 



Micrabacia. Simple, free, discoidal, base concave. Colu- 

 mella false. Septa numerous, with their outer edges perpendicular. 

 Synapticulse present. Theca on the base only, thin ; costse granular. 

 Upper Cretaceous. Ex. M. coronula. 



G-oniopora ( = Litharcea). Compound, massive. Calyces more 

 or less polygonal. Septa well developed, the faces spiny, the upper 

 edges dentate. Walls of the corallites reticulate. Columella formed 

 by the ends of the septa. Cretaceous to present day, common in the 

 Eocene. Ex. G. websteri, Bracklesham Beds. 



ORDER II. ALCYONA.RIA 



The Alcyonaria are nearly all colonial organisms ; the 

 polyps possess eight mesenteries and eight tentacles, the 

 latter being provided with pinnules (fig. 36, 4). In the 



