MARYLAND GEOLOGICAL SURVEY 229 



have the lower margin of the aperture prominently elevated. There are 

 from 8 to 16 longitudinal series of cell-apertures around the segments; 

 seven of the transverse series occupy the space of .1 inch. Longitudinal 

 sections show that the cells radiate from a central axis, that their walls 

 are thin near the axis, and become much thickened as they approach the 

 surface. No diaphragms. In transverse sections the cells radiate from 

 the central axis, and appear as so many wedges arranged around a central 

 point." Ulrieh, 1893. 



Occurrence. CHAMBERSBURG LIMESTONE (Echinospherites bed). 

 Pinesburg Station, Maryland. Lebanon limestone division of the Stones 

 Eiver group at Lebanon and other localities in Central Tennessee. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Family RHINIDICTYONIDAE 



Genus RHINIDICTYA Ulrieh 

 RHINIDICTYA NEGLECTA Ulrieh 



Plate XLIV, Figs. 11-14 



Stictopora paupera (in part) Ulrieh, 1886, Fourteenth Ann. Kept. Geol. Nat. 



Hist. Surv. Minnesota, p. 69. 

 Rhinidictya neglecta Ulrieh, 1893, Geol. Minnesota, vol. iii, p. 130, pi. v, 



figs. 22-25. 



Description. " Zoarium small, branches dividing dichotomously at 

 intervals of from 4 to 7 mm., rather convex, the margins parallel, not 

 very sharp, and with non-cellulif erous border variable. Width of tranches 

 rather constant at about 1.5 mm. Zocecia in 8 to 11 ranges, the usual 

 number nine, with rather small, elliptical, oblique apertures, about 17 in 

 5 mm. lengthwise, and six in 1 mm. transversely. In most cases all the 

 apertures are directed longitudinally or parallel with the edges of the 

 branches; in others, however, those forming the marginal row on each 

 side may be turned slightly outward. Interspaces comparatively thick, 

 less ridge-shaped than usual, often slightly zigzag, with the range of 

 granules well developed. 



" Internal structure chiefly diagnostic in vertical sections. These show 

 that the primitive or prostrate cell is comparatively elongate, and that at 



