COKALS OF THE CINCINNATI GROUP. 209 



which have the form of small, flattened fronds, about an inch or an inch 

 and a half in height, and three-quarters 'of a line in thickness, which 

 would appear to be probably young examples of this form. 

 Position and locality : Cincinnati group, Cincinnati, Ohio. 



ChvEtetes clathratulus, James. 



Plate 22, figs. 2, 25. 



Stictopora daihratula, James ; Cat. of the Lower Sil. Foss. of the Cincinnati group, 

 1871. (Named, but not figured or described.) 



Corallum forming a thin, undulating expansion, of unknown but con- 

 siderable size, and from half a line, or less, to nearly a line and a half in 

 thickness. The frond evidently grew in an erect position, as it consists 

 of tw^o layers of corallites which have their bases fixed to a common 

 calcareous membrane, and open on opposite sides of the corallum. The 

 corallites thus vary from less than a quarter of a line to over half a line 

 in height, and they are slightly oblique to the surface and to the central 

 lamina. The calices are somewhat oblique, the lower lip sometimes 

 very slightly prominent, the walls moderately thick, for the most part 

 altogether equal in size, about ten in the space of one line, arranged in 

 very regular diagonal lines, which are disposed in two sets crossing the 

 corallum from side to side and intersecting at acute angles. Surface, 

 with low, rounded, and obscure elevations, arranged in diagonal rows at 

 intervals of from a line to a line and a half, and occupied by corallites 

 which are either no larger, or but slightly larger, than the average. 

 There is a total and entire absence of minute interstitial tubules between . 

 the corallites. 



This beautiful fossil at first sight might be taken for one of the ex- 

 planate Ptilodictyx, though clearly not of this nature. I have not, how- 

 ever, been able to satisfy myself as to its possession of tabular, and am 

 thus not altogether certain as to its generic aflSnities. In the form of 

 the calices, however, and more especially in the presence of low tubercles, 

 it fully resembles Chsetetes, and I have little doubt as to its being prop- 

 erly placed in this position. It is distinguished from the other frond-- 

 escent species of Chsctefes by the arrangement of the calices in regularly 

 intersecting diagonal lines, by the fact that the tubercles are not only 

 very low, but are not occupied by corallites which are conspicuously 

 either larger or smaller than the average, and by the complete absence 

 of small tubes amongst the ordinary corallites. 



Position and locality : Cincinnati group, Cincinnati, Ohio. Collected by Mr. U. P. 

 James. 



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