186 PEor. p. MAETiK dukcan's eeyision op the 



G-enus Pbiscitueben-, Eunth, Zeits. der Deutsch. Geol. GesellscJi. 

 Bd. xxii. p. 25 (Berlin, 1870). 



Colony low, expanding, attached by the whole base. Coenen- 

 chyma well developed, compact, and composed of a sponge-like 

 structure. Calices projecting, rather inclined, differing in size, 

 nearly or quite circular in outline, surrounded by coenenchyma. 

 Septa variable, both thick and thin. Columella spongy. 



Distribution. — Fossil. Silurian : Oeland. 



This is a very puzzling genus, and its characters have been 

 very ably described and delineated by Kuntb. Its position is 

 probably amongst the Turbinarinse. 



G-enus Sttlae^a, SeebacJi, Zeits. der Deutsch. Geol. Gesellsch. 

 Bd. xviii. p. 306 (Berlin, 1866). 

 Colony low, covering some space, with a crust-like, vermiculate, 

 perforated coenenchyma and a basal epitheca. Calices polygonal, 

 moderately deep, with a stout, projecting, spongy columella. 

 Septa strongly crenulate, in two cycles. Walls moderately stout, 

 bearing points in the angles of the calices. 



Distribution. — Fossil. Lower Silurian : Europe (Wesenberg). 



III. Family PORITID^E, Ed. ^ H. 



Perforate Madreporaria composed of reticulate and trabeculate 

 sclerencbyma. Septa never completely lamellary, but trabecular 

 and fenestrated, or as series of discontinuous trabeculae. Walls 

 very porose. Corallites increasing by gemmation, and united 

 directly or by intervening porous sclerencbyma. Dissepiments 

 and tabulae may exist. 



There are two Alliances — tbe Poritinoida and the Montiporoida. 



I. Alliance PORITINOIDA. 



Corallites united by their trabeculate walls without intervening coenen- 

 chyma, or with some of very rudimentary kind. 



Genus Porites, Ed. & H. 



Genus Synar^a, Verrill. 



Genus Napopora, Quelch. 



Genus Dictyar^a, Reuss. 



Genus Rhodar.ea, Ed. & H. 



Genus Goniopora, Quoy et Gaimard. 



Genus LiTHABiEA, Ed. & H. 



