58 ACTINOZOA. MADREPORARIA. 



marked septal fossula, containing a septum which is 

 generally small. Septa numerous. Tabulae well developed, 

 extending quite across the visceral chamber. Dissepiments 

 few, never forming a peripheral vesicular zone. Columella 

 absent. Theca thick. Wenlock Limestone to Carboni- 

 ferous Limestone. 



Calceola. Simple, conical or slipper-shaped, one side 

 is flat, the opposite convex ; calyx very deep and closed 

 by a semi-lunar operculum, which has on its inner surface 

 a strongly marked median ridge and several less prominent 

 lateral ridges. Septa rudimentary, being represented by 

 striae. An epitheca is present. Middle Devonian. 



Section III. Fungida. 



The corallum is simple or compound. The calyces are 

 united by their costa3. Synapticulae are present, and 

 sometimes also a columella and dissepiments. Septa 

 generally solid. 



Thamnastraea. Compound, massive ; convex or 

 laminar. Walls of the corallites indistinct. Calyces 

 shallow. Septa of adjoining corallites confluent. Colu- 

 mella variable. Dissepiments and synapticulae present. 

 In England, Lias to Upper Greensand ; foreign, Trias to 

 Miocene. 



Section IV. Perforata. 



The corallum is porous or reticulate. The visceral 

 cavities of adjoining corallites are placed in communication 

 with one another by means of perforations in their walls. 

 The septa sometimes consist of trabeculae, or are repre- 

 sented by spines only. Dissepiments and tabulae may or 

 may not be present. 



