Palceozoic Corals of the State of Ohio. 89 



which might readily be taken for young forms of G. petropo- 

 litanus. The characters shown by sections would appear, how- 

 ever, to render this hypothesis untenable, or, at any rate, un- 

 likely. As seen in transverse sections (PI. V. fig. 7), the 

 corallites are irregularly polygonal or rounded, with thick 

 walls, and having numerous small tubes scattered amongst 

 those of the ordinary size. In vertical sections (PI. V. fig 7 a), 

 the corallites are seen to be directed upwards from the basal 

 concave epitheca, with a slight oblique curvature. Their walls, 

 at first thin, become thickened in approaching the surface ; and 

 their interior is crossed by delicate and comparatively remote 

 tabulae. Small tubuli are occasionally interspersed amongst 

 those of the usual dimensions ; and these are more closely 

 tabulate than is the case with the full-sized corallites. It will 

 thus be seen that, both in horizontal and vertical section, 

 C. discoideus differs greatly from adult examples of G. petro- 

 politanus. 



Ghcetetes Newberry i^Wi^\o\&or\, op. cit. p. 212, pi. 22. 

 figs. 4, 4 a. 



In external form this species is superficially very like 

 G. discoideus, James ; but its more minute external characters 

 are very different, and these differences are fully borne out 

 by an examination of the internal structure of both forms. 

 The corallites appear, in transverse sections (PL V. fig. 8), 

 as approximately circular tubes of nearly equal size, and 

 arranged in regular rows, those of contiguous rows being 

 sometimes placed opposite each other, sometimes alternately. 

 The Avails of the corallites are thick ; and at every point 

 where four corallites come together is placed a small cir- 

 cular tube. Every corallite, therefore, is surrounded by four 

 of these smaller tubuli. In vertical section (PI. V. fig. 8 a), the 

 corallites are directed upwards with a slight curvature from 

 the attached base, each being furnished with a few regular 

 and remote tabulae. Interspersed with the ordinary corallites 

 are minute tubuli, with numerous close-set tabulae. In this 

 latter feature, this species, as is the case with several other 

 species of Ghcetetes {Monticulipora) ^ reminds one forcibly of 

 the Heliolitidge. 



Ghcetetes Jamesi, Nicholson, op. cit. p. 200, pi. 21. 

 figs. 11, 11 a. 



The internal structure of this fine species is very charac- 

 teristic. In the centre of the corallum, as seen in vertical 



