168 



Cincinnati Society of Natural History. 



Stictopora, Hall. 



Zoarium attached to foreign objects by an expanded base, ramose, 

 branches compressed, and composed of two layers of cells, which open 

 upon the two flattened faces of the branches, and have their bases 

 brought into juxtaposition by the adhesion of their epithecal laminae. 

 Branches with an acutety elliptical transverse section, from less than 

 .1 of an inch, to sometimes a little more than .2 of an inch in width ; 

 the edges are marked by a more or less distinct non-poriferous margin. 

 Cell-apertures oval or circular, usually arranged between raised longi- 

 tudinal lines, with the interspaces smooth, rarely finely striate. Thin 

 sections show that the tubes are of one kind only, with walls very thin 

 near the median laminae, but much thickened just below the surface; 

 between the rows of cells are dark lines, indicating the raised longi- 

 tudinal lines observed on the surface of the branches. 



This genus has usually been considered, either as an exact synonym 

 for Ptilodictya, Lonsdale, or as based upon types only sub-generically 

 distinct from typical species of that genus. That I regard both these 

 views as erroneous, I need scarcely say, since my opinion of the 

 relations of these forms is amply shown in the foregoing scheme of 

 classification. 



As I have before stated, I consider the differences between Ptilo- 

 dictya and Stictopora to be not only of generic importance, but of suf- 

 ficient value to constitute the basis for the establishment of a separate 

 and distinct family, for which 1 have proposed the name of Sticto- 

 poridai. 



Stictopora acuta, Hall. (PI. VIII., figs. 1, la and 16.) 



Stictopora ? acuta, Hall, 1847. Pal. N. Y., vol. i., PI. XXVI., fig. 3. 



This species is a common- fossil in the upper strata of the Trenton 

 group, at Burgin, Ky., on the line of the Cincinnati Southern Railroad. 

 The Kentucky specimens differ from typical New York examples, in 

 being somewhat more robust. In all other respects they are the same. 

 Hall in his original description of the species, expressed a doubt 

 whether a central axis was developed. A central axis or lamina is 

 present in the same sense as it is in all double-leaved Bryozoa known 

 to me. That is, the two adhering epithecal membranes constitute an 

 " axis" from which the cells proceed in opposite directions. 



Stictopora gilberti, Meek. (PI. VIII., figs. 2 and 2a.) 

 Ptilodictya (Stictopora) gilberti, Meek, 1871 ; Proc. Acad. Nat. 

 Sci., Phil., p. 7 ; and Pal. Ohio, vol. 1, p. 194, 1873. 



