28 Cincinnati Society of Natural History. 



embryo or a cilated animalcule floating free in the water, and giv- 

 ing rise to a colony by generation from either side and from one 

 end, leaving the other as a central tube or cavity. Nicholson, 

 amon^ others, considers it to have taken its form from something 

 inherent in itself, and not due to growing around any other object. 

 Formation and Locality. — Lower Silurian, Cin. Group, Cin- 

 cinnati, Ohio. 



Sub genus A. 



Dekavia, Edw. & Haime, 1851. 



Pol. Foss. des Terr. Pal. 277 p. iJ?5i; Nicholson, Pal. Tab. 

 Cor., 291, 297, 1879. The Genus Montic, 98, 1881 Ulrich, 

 Jour. Cin. S. N. Hist. V, 155, 1882; VI, 148, 1883. 



Dekayclla mxich. Jour. C.S.N. H., V, 155, 1882; VI, 

 90, 1883. 



Corallum branching, with corallites of two kinds, the smaller 

 isolated by the larger tubes. Large calices polygonal, thin walled. 

 Small ones with thickened walls, and with conspicuous, blunt, 

 spine like processes at the angles of junction of the larger tubes. 



This sub-genus can only be separated from Monticulipora by 

 the surface columns, which constitute a marked feature of the 

 exterior. 



53 M. (Dekavia) aspera. Ed. & H. 



Pol. Foss, des Terr. Pal. 277, 185 1. 



Dekayia attrita, Nicholson. Pal. Tab. Cor. 298, 1879; Ann. 

 Nat. Hist. ser..4, XVIII, 93, 1876. 



C/ue/ctcs attritus, Nicholson. Quart. Jour. Geol. Soc. XXX, 

 503, 1874; Pal. Ohio, II, 194, 1875. 



Dekayia mactilata, U. P. James. The Palseon. 36, 1881. 



D. pelliculata, Ulrich. Jour. Cin. S. Nat. H. VI, 150, 1883. 



D. trentonensis, Ul. Ibid, 151; ^ 



D. apprcssa Ul Ibid, 152; 1 „„ 



D. paupera,V\. Ibid, 153; { '^^>5- 



D. multispinosa, Ul. Ibid 154. J 



CoralUim dendroid, branching dichotomously and frequently; 

 branches small, from three to ten lines in diameter, sometimes flat- 

 tened. Surface often with clusters of cells larger than the aver- 

 age scattered over the surface; monticules, when developed, occu- 

 pied at the summit by small cells. Calices polygonal, in some 

 cases covered with a pellicle which often hides the spinous pro- 

 cesses. Spines generally conspicuous, developed at angles of 



