/'a/coii/o/o,i;v of the Ciiiciniiali Croup. 151 



partially st-parated 1)\- iiiters])accs toward their luoutlis; calices 

 rounded or polygonal, about i '_• lines in diameter, olten with 

 smaller ones intercalated, the niar^^ins thick and crenulated 

 by the septa; septa about twent}-, more or less, forming 

 strong longitudinal ridges ])assing only a short distance 

 inward ; mural pores large, oval, arranged in rows between 

 the septa, separated generally by a space less than their own 

 diameter ; tabulae numerous, complete, flexuous, often uniting 

 with one another, about eight in the space of one line. 

 (Geol. Mag., new ser., vol. i, 1874, p. 253.) {Coliimnopoya 

 cribrifonnis, Nicholson.) 



Locality. — Cincinnati, O. 



Remarks. — As above noted, this species w'as originally de- 

 scribed as a Co/iinmopora, and it has been generally placed in 

 this genus. Dr. Nicholson has discarded his name in favor 

 of the older one, Calapixcia. 



vSub-claSS. — AlC VON ARIA. 



This sub-class is characterized by the possession of " polypes 

 with eight pinnately fringed tentacles, the mesenteries and 

 intermesenteric chambers being also eight in number. The 

 corallum is usually sclerobasic or spicular, or formed of both 

 an axial sclerobasis and detached spicules. In other types, 

 the polypes composing the colony ma}' be provided with 

 separate theca?."* The eight tentacles and eight mesenteries 

 chief!}' distinguish the sub-class from the ZoaiitJiaria. The 

 corallum is compound and variable in form, being branching, 

 linear, discoid, frondescent, etc., either fixed by a root-like 

 process or floating free. The corallites are tubular and the 

 tabuke well developed. 



There are numerous living and comparatively few fossil 

 genera, at least in our section. Indeed, there are but two occur- 

 ring, so far as knowai, in the Cincinnati Group in Ohio. These 

 have been referred to separate families, and constitute the 

 typical genera. They are Hcliolites placed in the Hclioliiida' 

 and Tetradiiim in the Tetradiidce. We give here the generic 

 and not the family characters. Hcliolites has one species, and 

 Tetradiiim two or three in our section. 



'■'Nicholson, Manual of Palteoii., vol. 1. ]s.s;), p. :\2.\. 



