On the Montlculiporoids of the Cincinnati Group. 169 



shape. Under surface flat or concave, covered with a con- 

 centrically striated epitheca. Corallites springing upwards, at 

 right angles to the base, and giving rise to an expansion thin at the 

 edges, and elevated in the centre from one-half an inch to an inch 

 above the base ; sometimes two elevations are present. Calices 

 thin walled, polygonal, nearly equal in size. Scattered over the 

 surface are clusters of slightly larger cells, either even with the sur- 

 face or raised slightly above ,it. Interstitial cells very few or 

 none. 



Obs. This is one of the forms formerly classed with M. 

 petropolitana, and one which would, perhaps, be best replaced 

 there. 



Var. WELCHi, U. P. James. 



Alonticulipora iyMonotrypd) welchi^ James. The Paltcont., 50, 

 1882. 



This variety has the same general mode of growth as the 

 typical form. The monticules are much more pronounced, and the 

 central portions are occupied by from four to ten or more small 

 pores, the larger calices surrounding or being mingled with these. 

 Interstitial cells are rarely found scattered among the calices 

 covering the general surface. One peculiar feature is to be found 

 in certain projections, either straight or branching, which spring 

 from the upper surface of the corallum. 



Formation and Locality. Lower Silurian, Cincinnati Gr. , 

 Cincinnati, O. 



13. M. WHiTEAVESii, Nicholson. 



Monticulipora {Diplotrypa) Whiteavesii, Nich., Genus Montic, 

 r6o, 1881. (pars), Nich., Pal. Tab. Corals pi., XIII. figs 4, 4^. 



Chcetetes petropolitanus, (pars) Nicholson, Quart. Jour. Geol. 

 Soc, XXX., p. 510, 1875. (pars) Pal. of Ohio, II., p. 204, 1875, 

 (pars) Geol. Mag. Dec. ii.. Vol II., 175, 1875. (pars) Ann. 

 Nat. Hist. ser. 4, XVIII. , 88, 1876; Kept. Pal. of Ont. 10, 



1875. 



Monticulipora [Frasopora) selwynii, Nicholson, Genus Montic, 



206, 1881. 



Prasopora simulatrix, Ulrich. 14th Ann. Rept. G. and N. H, 

 Sur. Minn., 85, 1886. 



P. conoidea, Ul. Ibid, 87. 



Diplotrypa infida, Ul. Ibid, 88. 



