888 PALEONTOLOGY OF ILLINOIS. 



ACROGENIA Hall. Hamilton. Founded upon a remarkable 

 species in which the zoarium is segmented very much as in 

 Dicranopora Ulr. 



COSCINELLA Hall. Hamilton. 



Family RHINOPORID.E n. fam. (Provisional.) 



RHINOPORA Hall. Zoaria bifoliate; forming large undulating 

 expansions, having the free lateral margins thickened and non- 

 poriferous. Surface without maculae or monticules, but when 

 perfect, exhibiting slender rounded bifurcating ridges, which, 

 when the zoariuin is a little worn, appear as shallow grooves. 

 The tubular structure thereby indicated is borne out by an ex- 

 amination of thin sections. These show further that they are 

 crossed by rather remote partitions. Zooecia apertures subcir- 

 cular, occupying the summits of prominent papillae, arranged 

 in more or less regular intersecting lines. Mesopores small, 

 about equal in number to the zocecia, sometimes showing at 

 the surface (?due to attrition). Large median tubuli between 

 the mesial laminae. 



Type: JR, verrucosti Hall. Range, Clinton and Niagara. 



Family STICTOPORID.E Ulrich. (Emended). 



Zoaria bifoliate, consisting of compressed branches, or leaf- 

 like expansions. Primitive cells subquadrate, arranged in longi- 

 tudinal series. Both primitive and superficial aperture elliptical 

 or subcircular, sometimes a little truncated posteriorly when 

 the superior hemiseptum is more than usually developed. In- 

 ferior septum wanting. Median tubuli present between the 

 median laminae, and the longitudinal rows of zooecia vestibules. 

 Mesopores absent, but vesicular tissue sometimes present. 



STICTOPORA Hall, (Rhinidictya Ulricn). Zoaria composed of 

 narrow, compressed, dichotomously divided branches, with the 

 margins sharp, straight and essentially parallel; attached to 

 foreign bodies by a continuous expanded base. Zooecia aper- 

 tures sub-circular or elliptical, arranged alternately in longitu- 



