186 



PROF. P. MARTIN DTJNCAN's REVISIOT^ OF THE 



Grenus Priscittjrbeis', Kunth, Zeits. der Beutsch. Geol. GeseUsch. 

 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. 



Distrihiition. — Fossil. Silurian : Oeland. 



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

 very ably described and delineated by Kunth. Its position is 

 probably amongst the Turbinarinse. 



Genus Sttlar^a, Seehach, Zeits. der DeutscTi. 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 POEITID^, Ed. ^ H. 



Perforate Madreporaria composed of reticulate and trabeculate 

 sclerenchyma. Septa never completely lamellary, but trabecular 

 and fenestrated, or as series of discontinuous trabeculse. Walls 

 very porose. Corallites increasing by gemmation, and united 

 directly or by intervening porous sclerenchyma. Dissepiments 

 and tabulae may exist. 



There are two Alliances — the 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 Lithar^a, Ed. & H. 



