9 8 Cincinnati Society of Natural History. 



NEMATOPORA CONFERTA, n. Sp. 



Fig. 22. — Nematopora conferta, n. sp. Zoarium of this species, natural size, x9, and 

 portion of same magnified eighteen diameters. 



Zoarium ramose ; branches dividing dichotomously at intervals 

 of about 2 mm., 0.4 to 0.5 mm. in diameter, subcircular in cross- 

 section. Zooecia in five or six longitudinal ranges, their apertures 

 subcircular or broad-oval, frequently arranged also in rows encir- 

 cling the stems; slightly oblique, surrounded by a thin peristome, 

 strongest and most elevated posteriorly; diameter of apertures 

 0.15 mm., separated by intervals, longitudinally, greater than the 

 diameter, between seven and eight in 2.5 mm. Interspaces stri- 

 ated, occasionally rising into ridges which separate the longitudinal 

 ranges of zocecial apertures for a short distance. 



The smaller, subcircular apertures and simply striated inter- 

 spaces distinguish this species from N. ovalis. JV. alternata, Ulr., 

 from the Galena or Upper Trenton of Southern Illinois, has the 

 zocecial apertures arranged in quincunx. In JV. retrorsa, from 

 the same locality and formation, they are ranged between longitu- 

 dinal ridges. 



Position and locality : Top of Trenton Shales, Cannon Falls, 

 Minn. 



