BRYOZOA—CRYPTOSTOMATA. 1 59 



wanting; zooecia in 14 or 15 rows, the intervening ridges carry- 

 ing granules; apertures direct. 



Stones River to Trenton, Minnesota and Iowa. 



138. R. trentonensis (Ulrich). Ordovicic. 

 Marginal apertures generally somewhat larger; interspaces thin, 



without granules; superior hemiseptum not developed. 



Stones River of Tennessee, Minnesota, Wisconsin and Illinois. 



LXXXI. Phyllodictya Ulrich. 

 Bifoliate, simple or irregularly branched, from an expanded at- 

 tached base ; long tubular zocecia with diaphragms, but without 

 hemisepta, bending very gradually outward from central axis, form- 

 ing oblique apertures with posterior edge lip-like ; wide subsolid 

 interspaces, traversed vertically by minute tubuli, which appear as 

 papillae upon the surface. Ord. 



139. P. varia Ulrich. (Fig. 208,/) Ordovicic. 

 Leaf-like expansions, surface with smooth or finely granulated 



striate maculae at 4 mm. intervals; apertures pyriform, oblique, 

 with peristome strong posteriorly ; granulose vertical ridges be- 

 tween the apertures. 



Black River of Minnesota. 



LXXXII. Pachydictya Ulrich. 

 Bifoliate, ramose, of narrow, bifurcating stipes with parallel 

 margins ; or irregular undulating fronds with acute non-poriferous 

 margins ; surface with small maculae, surrounded by apertures 

 slightly larger than the average ; marginal rows of apertures some- 

 times larger than average ; zocecia thin-walled, elliptical or sub- 

 quadrate, separated by small vesicles ; vestibules direct, thick- 

 walled, ring-like in section ; interspaces with minute tubuli ; one or 

 more diaphragms present. Ord.-Sil. 



140. P. fimbriata Ulrich. (Fig. 214, a.) Ordovicic 

 Branches from 2 to 5 mm. wide, with subparallel, wavy or ruffled 



non-poriferous margins ; apertures in rows in central area, between 

 lines of minute pores. 



Black River of Minnesota and Stones River of Tennessee. 



141. P. acuta (Hall). Ordovicic. 

 Differs from the preceding in its smooth non-poriferous margin 



