92 ANTHOZOA. ZOANTHARIA 



operculum, which has on its inner surface a strongly -marked median 

 ridge and several less prominent lateral ridges ; septa indicated by 

 striae in the calyx ; wall thick. Middle Devonian. Ex. C. sandalina. 



Goniophyllum. Similar to Calceola, but quadrangular ; 

 operculum consists of four plates forming a pyramid over calyx. 

 Visceral chamber filled with vesicular tissue. Silurian. Ex. G. 

 Jletcheri, Wenlock Limestone. An operculum also occurs in 

 the allied genus Rhizophyllum, Silurian. 



2. Aporose Corals. 



Turbinolia. Simple, conical, free ; calyx circular, with pro- 

 jecting columella. Septa exsert. Costse lamellar, projecting, with 

 pits in the grooves between them. No dissepiments or tabulse. 

 Eocene and Oligocene (? Recent). Ex. T. humilis, Barton Beds. 



Flabellum. Simple, compressed, fan-shaped, free or fixed by 

 rootlets. Calyx narrow, deep ; septa numerous. Columella trabe- 

 culate. Costae smooth or spiny. Upper Cretaceous to present day. 

 Ex. F. woodi, Coralline Crag. 



Montlivaltia. (fig. 25.) Simple, fixed or free ; turbinate, 

 cylindrical, conical, or discoidal. Epitheca well developed, theca 

 thin. Columella absent. Septa numerous, strong, often exsert, the 

 upper edges dentate. Dissepiments abundant. Trias to Recent ; 

 in England, Lias to Corallian. Ex. M. trochoides, Inferior and Great 

 Oolite. 



Parasmilia. Simple, fixed, turbinate or elongate. Calyx 

 circular. Columella spongy. Septa well developed, exsert, granular 

 on the sides. Wall with costse. Cretaceous to present day. Ex. 

 P. centralis, Chalk. 



IsastraBa. Compound, massive ; calyces polygonal. Walls 

 of the corallites fused along their entire length. Columella rudi- 

 mentary or absent. Septa thin and close together. Dissepiments 

 abundant. Trias to Eocene; in England, Lias to Upper Greensand. 

 Ex. /. explanata, Corallian. 



Stylina. Compound, usually massive ; calyces circular, pro- 

 jecting, usually separated. Columella small, styliform. Septa exsert. 

 Dissepiments abundant. Corallites united by costse. Basal epi- 



