I/O Cincinnati Society of Natural History. 



Corallum discoid when young, liemispheric when adiiU, often 

 with wide margins; varying in size from one-half inch, to one and 

 one-quarter inches in diameter, and from two to six lines or more 

 high. Under surface with a concentrically wrinkled epitheca, 

 generally deeply concave, but sometimes flat. Upper surface 

 with scattered and very slightly raised monticules, composed of 

 corallites slightly above the average size. Coralhtes directed at 

 nearly right angles to the entn-e basal plate, to the upper surface, and 

 of two kinds, large and small, and both intermingled. Large tubes 

 more or less thin-walled, angular, sub-angular, or hexagonal, some- 

 times in groups of four or five each. Small corallites very 

 numerous and variable in size and form, always thin-walled and 

 angular, filling the spaces between the larger tubes. Spiniform 

 corallites at the angles of junction of the cells. 



Obs. This species is similar in form to AI. petasifonnis, Nich., 

 but differs in its numerous, angular interstitial cells, and the 

 presence of monticules. The species described as new by Mr. 

 Ulrich, as above, are the same as far as may be judged from 

 the descriptions, and it would be a puzzling matter to say just 

 what the distinctions between them are. M. selwynii, Nich., is 

 placed here as a synonym because it is utterly impossible to dis- 

 tinguish it from wliitcavesi ixovci the external form of the corallum, 

 the sole difference being in the interior structure. This is con- 

 sidered so important by Dr. Nicholson as to induce him to put the 

 two forms in different sub-genera. Specimens identified by us as 

 this species are much worn on the surface so the calices do not 

 show well, but we feel reasonably sure of the identification. 



Formation and Locality. Lower Silurian, Trenton Group. 

 Peterboro, Ontario; Minneapolis, St. Paul, &c., Minnesota; Ken- 

 tucky and Tennessee. Cincinnati Group, Warren and Clinton 

 Counties, &c., Ohio. 



14. M. ciNCiNNATiENSis, U. P. James. 



Monticulipora (^Peronopord) cincinnaiicnsis^ James. Nicholson, 

 Genus Montic, 226, 1881. 



Ch(Btetes cinciniiatiensis, ]dimes. Cat. Low. Sil. Foss. , 2, 1875. 



]\'±onticulipora consimilis, Ulrich, Jour. Cin. Soc. N. Hist. V., 

 238, 1882. 



Prasopora nodosa, Ulrich, Ibid, V. 245, 1882. 



Corallum either free or attached, forming a layer a line or less 

 thick. Under surface with a strongly wrinkled epitheca, not often 



