86 



Cincinnati Society of Natural History. 



foreign bodies, generally the shells of brachiopods (Strophomena 

 alternata, etc.) ; more or less convex above ; surface generally smooth, 

 but often with a single central elevation ; calices sub-circular, mostly 

 equal, with moderately thick walls ; no interstitial cells ( Pal. of 

 Ohio, vol. 2, 1875, p. 213, as Ckcetetes.) 



Locality. — Cincinnati, O,; Kentucky and Minnesota. 



Remarks. — This peculiar little species can scarcely be mistaken 

 for any other. " It is questionable whether it may not be the base of 

 some other species, possibly the young corallum of some incrusting 

 form like M. papillata. Nicholson, indeed, makes such a suggestion 

 but does not think it likely. He says further that ' at any rate in the 

 absence of any specimen by which this could be directly connected 

 with any other known form, I have thought it best to place it under a 

 separate title, since it is not only common in its occurrence, but is 

 also very constant in its size and other characters.' " Mr. Ulrich has 

 placed it in his genus Petigopora. I have not been able to find any 

 description of its internal microscopic characters. 



7^.— M. selwynii Nicholson, 1881. 



Corallum varying from 1^ to 3^ inches in diameter and about 

 one-half inch high in the centre ; discoid or conical, base flat or con- 

 cave, covered by a concentrically striated epitheca; corallites of two 

 kinds, larger oval or irregularly circular, sV to ts inch in diameter, 

 smaller, interstitial ones, angular or sub angular, from 2<ro to xio inch in 

 diameter, and collected at intervals into maculae ; surface smooth ; 

 tabulae in larger tubes more or less convex and forming a series of 

 vesicles on one side of the chamber, while others run from these 

 across to the opposite side, or across directly from side to side ; tabulae 

 in the small tubes numerous, closely set, complete and horizontal. 

 (Genus Montic, as Prasopora, 1881, p. 206.) [Prasopora simulatrix 

 Ulrich, 14th Ann. Rept. Minn. Geol. & Nat. Hist. Sur., 1886, 

 P. 85.) 



Locality. — Canada, Minnesota, Kentucky and Tennessee. 

 (Trenton.) 



Remarks. — There are not enough differences between Nicholson's 

 selwynii and Ulrich's simulatrix to justify a separation. Although 

 this is a Trenton species it is inserted here with the idea of its possible 

 occurrence in the Cincinnati group. Nicholson's M. {Prasopora) 

 selwynii var. hospitalis is the same as M. turbinata James. This was 



