American Palaeozoic Bryozoa. 



171 



the cell-apertures occupy the summits of small transverse ridges, nine 

 of which occupy the space of .2 inch. Where a branch has a width of 

 .2 inch, there are in all fourteen longitudinal rows of cells. At the 

 surface no interstitial cells can be detected, the space between the 

 cell-apertures being smooth. 



Longitudinal sections show that the tubes, in the axial region, are 

 thin-walled, and prostrate for about one half of their entire length, 

 when they bend abruptly outward and proceed directly to the surface. 

 The intertubular spaces, having a width equaling twice the diameter 

 of the tubes, are occupied on each side of the axial or epithecal mem- 

 branes, to the point of outward bending of the tubes, by vesicular 

 tissue; and above that point to the surface, by dense, irregularly 

 laminated sclerenchyma. 



In tangential sections the transverse section of the tubes is sub- 

 piriform; this appearance is produced by two slight inflections of 

 the walls of the tubes, which are placed opposite to each other, but a 

 little either to the right or the left of the longitudinal diameter line, 

 in such a manner that the smaller end of the piriform tube sections of 

 one side of a branch, are directed toward the right, and on the other 

 side, toward the left non- poriferous margin. Just below the surface 

 the intertubular spaces are occupied by sclerenchyma, with numerous 

 small, dark spots scattered through it, indicating a poriferous condition 

 for the thick interstitial membrane. Nearer the axial lamina? one or 

 two series of interstitial cells surround each tube. 



Beside C. occellata, I have examined three other species that must 

 be referred to this genus. Two of these are new, and the third was 

 described by Meek under the name of Ptilodictya ( Stictopora) car- 

 bonaria (Pal. Ohio, vol. ii., p. 328). Meek's species differs from the 

 one above described, in having more slender branches, and only from 

 seven to nine longitudinal series of cells, which are arranged simply in 

 diagonally intersecting lines, without the marginal transverse grooves 

 and rows of cells, which constitutes such a marked feature of C. occel- 

 lata. In all of the four species the internal structure is essentially 

 the same, acd the inter apertural spaces are without interstitial cells. 



Formation and locality: Collected near Somerset, Kentucky, in Sub- 

 carbonilerous strata, probably of the Keokuk group. 



Ph^enopora. (?) multipora, Hall. (Plate VIII., figs. 7, 7a, and 76.) 



Phcenopora multipora, Hall, 1851, Geo. Lake Sup. Land. Dist , 

 vol. ii. 



Zoarium consisting of rather large, thin, irregularly branching 



