11 



Cincinnati Society of Natural History. 



separated by interlaminar spaces, filled with minute vertical tubes. It 

 is destitute of the larger orifices and canals that usually occur in 

 Stromatopora, and I have been unable to ascertain that the concentric 

 lamina} are perforated by canals; they are apparently more dense than 

 the intervening spaces, but it is not supposed that the} 7 constituted a 

 barrier to the circulation. The sponge appears to consist of minute 

 tubes radiating from a central point, in all directions; these are cut 

 short by a laminar covering, which forms a basis for the minute radi- 

 ating tubes to spread in all directions, from its outer surface, until they 

 are likewise arrested by another covering, which, in turn, forms the 

 basis for radiating tubes, and so on to the 10th or 15th covering. 

 These coverings appear in cut and weathered specimens as irregularly 

 concentric lamina?. In magnified sections it shows an apparent vesic- 

 ular structure, but no spicules have been determined. I have referred 

 the species to Stromatocerium because it agrees with that genus in its 

 general texture, and seems to be destitute of the larger canals and su- 

 perficial openings that characterize the genus Stromatopora. 



It occurs in great abundance, in some of the rocky strata, in the 

 upper part of the Hudson River Group, at Richmond, Ind. Dr. John 

 T. Plummer, in a communication to the American Journal of Science, 

 many years ago, called the specimens "pisolitic balls embedded in the 

 solid rock." He said, these pisolitic strata vary from two to ten feet 

 in depth, and are frequentty found blended with the marlite. How- 

 ever, I did not find them in such massive strata, but there are some 

 la3'ers of rock about three or four inches in thickness, largely made up 

 of specimens of this little sponge, that may be found on the high 

 ground immediately above the railroad bridge, in the northern part of 

 the city. It is found at other places, in that locality, and may be re- 

 garded as a common species. 



Dystactospongia, n. gen. 



[Ety. — Dystaktos, hard to arrange; Sponqia, a sponge.] 



This is a massive, more or less regular! y hemispherical, fixed, calcare- 

 ous sponge. It possessed a strong frame work that radiated from 

 one or more points of attachment, and bifurcated without any deter- 

 minable order so as to constitute a great part of the body of the 

 sponge. The entire mass is vesicular, the frame work being more 

 dense than the intervening spaces. Spiculaa not ascertained. 



