COEALS OF THE CINCINNATI GROUP. 201 



examples, dividing dichotomously at varying intervals, irregularly thick- 

 ened and nodulated. Corallites oval, circular or sub-polygonal in section, 

 of unequal sizes. The larger corallites are about six in the space of one 

 line, with extremely thick walls, the margins of the oval or rounded 

 calices being generally obscurely tuberculated or granulated. The large 

 corallites are occasionally separated by extremely minute cylindrical 

 tubuli, which vary in number in different specimens or in different parts 

 of the same specimen, their presence, however, usually being little con- 

 spicuous. The surface exhibits no eminences or tubercles of any kind, 

 nor are there any groups of large sized corallites; but typical specimens 

 exhibit at irregular intervals stellate spaces, which are either solid or 

 minutely punctate, and which have a diameter of about two-thirds of a 

 line. 



This species is very nearly allied to Chxtetes tumidus, Phillips, especially 

 in the rounded and thickened corallites, separated by minute cylindrical 

 tubules. Chsetetes Jamesi, however, is distinguished by the larger size and 

 greater thickness of the ordinary corallites, by the smaller development 

 of the system of minute intermediate tubuli, the obscurely tuberculated 

 margins of the calices, and the general existence of stellate, solid or 

 pitted, vacant spaces. The value of the last of these characters is dimin- 

 ished by the fact that some specimens, in other respects the same, do not 

 exhibit these spaces in a conspicuous manner. Even in the absence of 

 these, however, the species can very readily be recognized by the extra- 

 ordinary thickness of the walls of the corallites, in which respect it is 

 not approached by any other form which occurs in the Lower Silurian 

 rocks. 



I have named this species in honor of Mr. U. P. James, who has col- 

 lected the organic remains of the Cincinnati group with the greatest per- 

 severance and judgment, and who kindly furnished me with specimens 

 for examination. 



Locality and position : Cincinnati group, Cincinnati, Ohio. 



Ch^tetes rhombicus, Nicholson. 



Plate 21, figs. 12, 12a. 



Corallum ramose, the stems hollow or solid, sub-cylindrical, from four 

 to six lines in diameter, terminating in acutely pointed, or, at other 

 times, in swollen and bulbous extremities. Corallites with very thin 

 walls, about eight or ten in the space of one line, variable in form and 



