On the Montictiliporoids of the Cincinnati Group. 163 



4. M. IRREGULARIS, Ulrich. 



Chxtdes i/'fegu/aris, Ulrich. Jour. Cin. Soc. Nat. Hist., Vol. 

 11., 129, 1879. 



Mo not rypa irregularis, Ulrich. Jour. Cin. Soc. N. H., V. 256, 

 1882. Nicholson, Genus Monticu p. 177, 1881. 



Corallum small, three fourths of an inch in diameter, ap- 

 parently free. Generally spheroidal, the surface covered with 

 irregular and well marked nodules. Corallites of one kind only, 

 thin-walled, polygonal. No monticules or groups of large or small 

 corallites. Tabulre almost absent, but when present developed at 

 corresponding levels in contiguous tubes as in M. uiidiilata, Nich. 



Obs. This species is similar in shape to M. tiirbinata, James, 

 but is easily separated by the nodulated surface, and much smaller 

 corallites. One of us has a specimen with a conspicuous pointed 

 base, and a puff-ball hke form, the upper surface irregularly 

 nodulated. Still another specimen is about one and one-quarter 

 inches in diameter, with six conspicuous divisions above, the sur- 

 face of these being entirely smooth. 



Formation and Locality. Lower Silurian, Cincinnati Gr., 

 Hamilton, Morrow, etc., Ohio. 



(}roupH. Discoid: Free, plano-convex, concavo-convex, or 

 conical; the upper surface bearing cell appertures, the lower cov- 

 ered with an epitheca. 

 a. Corallum concavo convex. 



* Epitheca concentrically lined or wrinkled. 



J Cells generally similar, 5. 



t Clusters of larger cells, 6, 7, 8. 



* Epitheca with lines radiating from the centre, 9. 



^ Epitheca with lines radiating from one point at the 

 side, 10. 



* Epitheca with a groove, 11. 

 /;. Corallum conical. 



* Edges thin. 



t Epitheca concentrically wrinkled, 12. 

 t Epitheca with a groove, 11. 



§ Monticules small, 13. 



§ Monticules prominent, 14. 



5. M. DiscoiDEA, U. P. James. 



Monticulipora (Monotrypa) discoidea,]a.Vi\t%. Nicholson, Genus 

 Montic, 193, 1 88 1. 



