184 



Cincinnati Society of Natural History. 



RHINIDICTYA EXIGUA, n. Sp. 



Fig. 9. — Rhinidictya exigua, n. sp. a, basal portion of zoarrum, natural size and xy : 

 near the base the zooecial apertures mostly closed by a secondary deposit : b, a very 

 narrow specimen with only three rows of cell apertures : c a wide example, having 

 five and six rows : d, lower portion of same x9. 



Zoarium bifoliate, small; branches, except near the base, thin 

 and very slender, their width varying between 0.5 and 1.0 mm.; 

 bifurcating at intervals of 5 or 6 mm. Basal portion of zoarium 

 subcylindrical, and with the zooecial apertures largely filled with a 

 smooth, solid deposit of sclerenchyma. The branches, however, 

 soon become flattened and sharp-edged, but at no time is there 

 more than just an appreciable noncelluliferous border. Above the 

 first bifurcation the branches are acutely elliptical in cross section, 

 and exhibit from three to six rows of zocecia on each face. The 

 apertures of the zocecia are impressed subelliptical or subquadrate, 

 those in the central rows 0.2 mm. long by 0.1 mm. wide, those in 

 the marginal rows oblique and often a little larger, all regularly 

 arranged longitudinally, seventeen or eighteen in 5 mm. Inter- 

 spaces very thin, about equal at the sides and ends of the zooecial 

 apertures, smooth (without granules) so far as observed. 



The characters relied upon in distinguishing this species are its 

 narrow branches, thin interspaces, small zooecia and comparatively 

 large apertures. It is closely related to i?. paupera (Stictopora 



