170 



Cincinnati Society of Natural History. 



Rhixidictya nicholsoni, nov. gen. et sp. (Plate VIII., figs. 6, 6r< 



and 66.) 



jRhinidictya, gen. char, ante, p. 152. 



Zoarinm slender, branching at intervals of from one half an inch to 

 one inch. Branches varying in width, in the extremes of the exam- 

 ples noticed, from .07 inch to .12 inch; in thickness, from .02 inch to 

 .04 inch. Cells small, with oval apertures, which in young examples 

 are somewhat oblique; the cell- walls, which with age become much 

 thickened, cany a closely arranged series of small spines or granules, 

 which tangential sections show are the surface extensions of small 

 spiniform tubuli. The cells are regularly arranged in alternating 

 longitudinal series, of which there are from ten to fourteen in the 

 width of the branches of the different specimens examined. Meas- 

 ured longitudinally, seven cells occupy the space of .1 inch ; transversely, 

 there are seven of the alternating longitudinal rows in .05 inch. 



Young nor worn specimens do not show the spiniform tubuli, and 

 for that reason Mr. U. P. James has described a Cincinnati species of 

 this genus under the two names of Ptilodictya granulosa, and P. par- 

 alella. Mr. James' species is in all respects more delicate, nor does it 

 appear to be so variable in its characters as the Trenton group species 

 above described. 



Named in honor of Dr. H. Alleyne Nicholson, whose numerous works 

 have added so much to our knowledge of the Palaeozoic Corals and 

 Bryozoa. 



Formation and localit} T : Trenton group, at High Bridge, Ky., a sta- 

 tion on the Cincinnati Southern R.R. 



Cxstodictya occellata, nov. gen. et sp. (Plate VIII., figs. 3, 3a). 

 Cystodictya, gen. char., ante p. 152. 



Zoarium branching at intervals of from .25 inch, to .80 inch ; width 

 of branches from .15 inch to .20 inch ; thickness of same about .04 

 inch. Non-poriferous margin smooth, not very acute, rather narrow. 

 Cell -apertures circular, occupying the summits of small papilla?, fre- 

 quently closed by centrally perforated opercula. In the central portion 

 of the branches the cells are regularly arranged in longitudinal and 

 intersecting diagonal series; measured longitudinally, six cells occupy 

 the space of .01 inch ; in the same space diagonally there are seven. 

 Along the edges of the branches there are several rows of cells, 

 which are somewhat larger than those over the central portion, and 

 which have a transverse arrangement; between these transverse series 

 of cells the surface is depressed into distinct and wide grooves, so that 



