1 6 Cincimiati Society of Natural History. 



Homotrypa dmvsoni, Nirh. Ulrirh. Jour. Tin. S. Nat. Hist.. 

 V 241, 1882. 



Corallum irregularly lobate or frondose, f> -ming an undulated 

 expansion of variable size, about two lines thick: Surface with 

 numerous close-set. prominent monticules, markedly elongated, 

 about a line or less apart, and occui)ied by corallites not differmg 

 conspicuously in size from those forming the mass of the corallum. 

 Galices polygonal, thin walled, nearly vertical from a central axis. 

 and opening on either side ; no regular series of small apertures, 

 but occasionally a few spiniform corallites at angles of junction of 

 cells. \\'alls delicate, wrinkled, slightly thickened toward mouths 

 of cells. 



Obs. — This is similar to the next, /iia/iiiiiulata, but seems to 

 differ in the more prominent, elongated and closely set monticules. 



Formation and Locality. — Lower Silurian, Cincinnati Group, 

 \Varren and Clinton Counties, O. Rare at Cincinnati. 



37. — M. MAMMULATA, D'Orbigny. 



Prodr. de Paleont., I. 25, 1850; Ed. (!^ Haine, Brit. Foss. 

 Cor., 265, 1854; Ulrich, Jour. Cin. S. N. Hist., V. 234, 1882. 



Chcetetes iiianviiulatiis, Ed. & H., Pol. Foss. des Terr. Pal. 267, 

 1851 ; Nicholson, Quar. Jour. Geol. Soc, XXX, 508, 1874; Pal. 

 Ohio, H, 207. 1875. 



MonticuUpora {Heterotrypa) inammulata. Nich.. Pal. Tab. Cor., 

 294, 1879; Genus Montic, 104, i88i. 



M. {Perflfiopora) i/iolcsfa, Nich., Genus Montic, 224, 1881. 



Corallum in undulated expansions, two to six lines or more 

 thick, often consisting of several layers of corallites, diverging 

 from an imaginary plane and opening on both sides ; occasionally 

 massive. Surface with rounded, conical or elongated monticules, 

 either conspicuous or only slightly raised ; these occupied by coral- 

 lites either slightly larger or slightly smaller than the average: or 

 else t bedsides with full-sized, and the summit with smaller corallites. 

 Calices of two]kinds : large ones polygonal, or sub-[)olygonal, mod- 

 erately thickened at the surface : small ones moderately numerous, 

 intercalated between the larger tubes, variable in size and shape, 

 but always angular or sub-angular. Spiniform corallites variable in 

 number. 



Obs. — -This is a species about which there has been much dis- 

 cussion. It has been considered the type of the genus, as it was the 

 first one described by D'Orbigny, but as the original description 

 was very defective, discussion has arisen as to what really should 



