250 



Cincinnati Society of Natural History. 



Besides, 31. quadrat a is a much more robust species with branches 

 varying in diameter from three to six tenths of an inch. 



As before remarked, I can not at present consider the existence of 

 interstitial tubes in 31. subquadrata, as of more than specific importance, 

 in so far as it has reference to the separation of the species from 31. 

 quadrata. 



Formation and locality-: Cincinnati Group. I have collected this 

 species at Osgood, Ind., where the strata exposed are very near the 

 top of the formation, Also at Jackson, Blanchester, and Westborough, 

 where the beds exposed are at least 100 feet lower than those at Osgood, 

 Ind., and equivalent to a height of nearly 700 feet above low-water 

 mark in the Ohio river, at Cincinnati, O. 



Callopora elegantula, Hall. (Plate XI., figs. 6-66.) 



Callopora elegantula, Hall, Pal. N. Y., Vol. ii., p. 144, Plate XL., 

 figs, la-1?*, 1852. 



Zoarium ramose, consisting of subcylindrical branches from one to 

 two tenths of an inch in diameter, that frequentty divide dichotomous- 

 \y, and sometimes inosculate. Surface without monticules. Cells with 

 rather thin walls and circular apertures, that have a diameter varying 

 from ^th to -g^th of an inch. Often the apertures are closed by 

 opercula having a small central perforation, from which six or seven 

 small ridges radiate to the margin, giving the false appearance of a 

 septate aperture. Interstitial spaces of variable width, and occupied 

 by small angular interstitial cells, which often completely isolate the 

 proper cells. According to the width of the interstitial spaces from 

 four to six of the proper cells may be counted in the space of .1 inch. 



Tangential sections (Plate XI., fig. 6) show that the zoarium is 

 conspicuously divided into two sets of tubes, large and small. The 

 large tubes have rather thin walls, are nearly uniform in size, and 

 generally, circular in shape. The small or interstitial tubes are 

 usually angular, very variable in size and form, and often so numerous 

 as to form a complete zone around the large tubes, which usually 

 consists of one row, though sometimes an incomplete second row is de- 

 veloped. At other times they occupy only the triangular interspaces 

 formed by the junction of three of the large tubes. There is no 

 boundary line between adjoining tubes, the walls of all the tubes being 

 apparently fused together. These sections show conclusively that the 

 diaphragms, in at least the peripheral portion of the zoarium, represent 



