1 68 Cincinnati Society of Natural History. 



Corallum piano, or slightly concavo-convex, sub-circular, 

 small, fro:n one to two lines in diameter, and one-half a line or 

 less thick. Under surface often exposed in specimens imbedded 

 in the rock, flat or slightly concave; epitheca thin, with fine con- 

 centric lines, having a starting point near one margin. Fine lines 

 also radiate from the eccentric starting point to the margin. Bases 

 of corallites easily seen through the epitheca. Upper surface 

 gently convex, smooth. Calices circular, similar in size, with a 

 tew of the central ones slightly larger than the others. Walls 

 thin. Interstitial corallites few or numerous. (Plate 2, figs. 2ab c.) 



Obs. This species can be readily recognized by its small size, 

 and the radiating stride having an eccentric starting point near one 

 edge of the corallum. 



Formation and Locality: Lower Silurian, Cincinnati Group, 

 Cincinnati, O. 



11. M. FALESi, U. P. James. 



Jour. Cin. Soc. Nat. Hist. VIL, 138, 1884. 



Corallum free, oval or round; the upper surface low and con- 

 vex in the oval specimens, and steep and conical, with a small 

 apex in the round ones; varying in size from about one-half to 

 three-fourths of an inch in diameter, and from one-quarter to three- 

 quarters of an inch high. Margins thin and sharp. Under sur- 

 face peculiar in possessing a regularly outlined conical groove, ex- 

 tending nearly across the middle of the longest diameter, and with 

 a pointed end, the concave surface of the groove covered with 

 fine transverse striae. Calices circular and polygonal; stellate 

 maculae distributed irregularly over the surface, little or not at all 

 elevated, and sub-solid or with a larger cell in the center. Walls 

 of cells thin; interstitial cells and spiniform corallites few. 



Obs. The peculiar feature of this species is found in the con- 

 ical, sharp-pointed groove which extends across the under surface, 

 and which seems to be a constant feature. I'he low, oval speci- 

 mens seem to be young individuals. 



Formation and Locality : Lower Silurian, Cincinnati Group, 

 Danville, Ky. 



12. M. PETASiFORMis, Nicliolson. 



Monticidipora {Mo?wtrypa) pctasi/or?!iis, Nich., Genus Montic, 

 190, 1881. 



Corallum free, conical or discoidal, varying in size from one- 

 half inch to nearly two inches in diameter, and also variable in 



