226 PALAEONTOLOGY OF OHIO. 



in the size of the calices, it may, however, be referred with tolerable cer- 

 tainty to the former species. I am' not aware that this form has previ- 

 ously been detected in the North American continent. 



Position and locality : Clinton group, Clarke county, Ohio. 



Favosites venusta, Hall. 



Astrocerium venustum, Hall; Pal. N. Y., Vol. II., pi. 34, figs, la, li. 

 Favosites venusta, Nicholson and Hinde; Canadian Journ., 2d series, Vol. XIV., No. 

 II., 1874. 



Corallum forming large hemispherical or spheroidal masses, which are 

 usually composed of a succession of concentric layers, and generally have 

 a more or less flattened upper surface. Corallites slender, variable in 

 size, polygonal, rapidly increasing in number by fission, so that the mass 

 increases rapidly in size in proceeding from the base upwards. The 

 larger corallites are usually about half a line across, but they have many 

 smaller ones intercalated amongst them, the diameter of which varies 

 from the fiftieth of an inch up to half a line. The calices are hexagonal, 

 polygonal, or sub-cylindrical, and there are usually rudimentary septa in 

 the form of very short spiniform projections. The tabulae are complete, 

 straight or flexuous, from four to six occupying the space of one line. 

 Mural pores undeterminable. 



The genus Astrocerium was found by Hall (Pal. N. Y., Vol. II., p. 126) 

 to include corals precisely similar in most respects to the typical species 

 of Favosites, except that they possess spiniform septa. Septa, however, 

 are by no means wanting, even in the most characteristic species of 

 Favosites, as, at any rate, an occasional thing. If it could be shown, as 

 Hall seems to have believed, that the corals which he referred to Astro- 

 cerium are destitute of mural pores, then the genus might perhaps be re- 

 tained ; but in the meanwhile this has not been proved, and it is, there- 

 fore, impossible to separate Astrocerium from Favosites. 



The present species can readily be distinguished from F. Gothlandica, 

 Lam., by the small size of the corallites, and, the great inequality in their 



. dimensions. It most nearly resembles F. hemispherica, Yand. and Shum- 

 ard, of the Devonian series, but it is separated from it without difficulty 

 by its totally different mode of growth, and by the fact that the tabulae 

 are both more remote and complete. The species appears to have com- 

 menced its existence in the Clinton formation, but it attains its highest 



• development in the Niagara period. 



Position and locality : Clinton group, Yellow Springs, Ohio. 



