166 



Cincinnati Society of Natural History. 



Graptodictya nitida, n. sp. (PI. VIL, figs. 8 and 8a.) 



As will be seen by a comparison of the enlarged view of the surface 

 of G. perelegans (PI. VIII., fig. 3), with that of this species, the cellular 

 structure in the two forms is almost identical. G. nitida differs from 

 that species only in its mode of growth. It is dichotomously divided 

 at about .6 inch above the pointed extremity of the articular process, 

 and none of the examples which I have seen are again divided above 

 the first bifurcation. Besides, its zoarium is somewhat more slender 

 than that of G. perelegans. 



Locality and formation : In the Cincinnati group, five miles north- 

 west of Hamilton, O., in strata equivalent to a height of 550 feet above 

 low water mark in the Ohio river at Cincinnati. 



Dicranopora, nov. gen. 



Zoarium large when complete, composed of numerous small ligulate 

 joints. The segments are flattened, from one fourth of an inch to one 

 inch in length, with the edges sub-parallel to near the upper end where 

 they suddenly diverge, and are dichotomously divided into two short 

 branches, the ends of which are thickened and solid, and articulate 

 with the next succeeding segments. Cell-mouths ovate to subquadrate, 

 and arranged between raised longitudinal lines. Usually the cells in 

 from one to three rows along the margins have an oblique direction. 

 No interstitial cells. 



Type, Ptilodictya internodia, Miller and D}'er. (PI. VII., figs. 9, 9a.) 



The specimen illustrated by Messrs. Miller and D} T er is an abnormal 

 segment, being simple instead of bifurcated. That condition is fre- 

 quently found in D. internodia, but I have not yet seen an undivided 

 segment of an}' other species. Dicranopora will include probably all 

 of the ligulate species of Ptilodictya. 



Dicranopora lata, n. sp. (PI. VI., figs. 16, 16a.) 



The segments of this species are about one inch in length ; their 

 width at the lower or simple end is about .08 inch ; at the bifurcated 

 end the width is usually about .16 inch ; the greatest thickness rarely 

 reaches .03 inch. The two articulating branch lets are remarkably 

 short, being general^ only about .05 inch ; they are only indicated by 

 a narrow cleft in the widest end of the segment. Cells with thick 

 walls and very small oval apertures. There are about ten longitudinal 

 rows of cells near the lower end, and at least twenty just below 

 the bifurcation. Measured along the length of a segment eight cells 

 occupy the space of .1 inch. There are two rows of obliquely arranged 

 cell-apertures along each of the acute margins. 



