BRYOZOA. 399 



apertures and slight peristome, arranged in a sub-radial manner, 

 in single or double rows. 



Type: S. parasitica n. sp. Range. Chester to Upper Coal 

 Bfeasun 



Family PHYLLOPORINID.E n. fam. 



Zoaria retiform and consisting of anastomosing branches; at 

 other times dichotomously branched; celluliferous on one side, 

 the other finely striated. Zocecia tubular, rather long, often 

 with diaphragms. Without hemisepta. 



PHYLLOPORIXA n. gen. Zoaria consisting of somewhat irregu- 

 larly anastomosing branches, with from two to eight ranges of 

 zocecia on the celluliferous side. Reverse convex, longitudinally 

 striated. Zocecia tubular, with or without diaphragms. Meso- 

 pores generally present, sometimes numerous, always closed at 

 the surface; with diaphragms. 



Types: Retepora trentonensis Nich., and E. asperato-stiiata 

 Hall. Range, Chazy to Niagara. 



CHAINODICTYON Fcerste. Much like the preceding but the 

 zocecia somewhat shorter. Mesopores and diaphragms wanting. 

 Reverse flattened, concentrically undulated or striated. 



Type: C. laxum Fcerste. Coal Measures. 



DRYMOTKYPA n. gen. Zoaria branching dic-hotomously at fre- 

 quent intervals. Reverse longitudinally striated. Zooecia in 

 several ranges, tubular,, thick-walled in tangential sections, 

 sj (ringing from a thin double plate, beneath which a number of 

 vesicles (? aborted zocecia) are present. Superficial apertures 

 angular, becoming oval a short distance within on account of 

 the thickening of the walls. 



Type: Retepora diffusa Hall, (Pal. N. Y. vol. II, p. 160). 

 Niagara group. 



The genus will also include Thamniscus cisseis Hall, (Lower 

 Held.) and T. niagarensis Hall. A fourth species from the Trenton 

 of Canada not yet described, I propose to name Drymotrypa 

 dichotoma* 



*Drymotrypa dichotoma n. sp. PI. LIII, flg. 6. Zoarium spreading in a plane, con- 

 sisting of frequently branching lax ramulets, one side of which is finely striated, the 

 other bearing the mouths of four ranges of zooecia; intervals between bifurcations 



