340 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Family 1. Phylloporinidae Ulrich. 



Zoaria branching, cellulijerous on one side only, the other side striated ; branches 

 free or anastomosing. Zooscia more or less tubular, often with diaphragms. Hemisepta 

 wanting. Ordovician to Coal Measures. 



a, h, Chasmatopora sublaxa (Ulr.). i'/l- 



Fk;. 497. 

 d, Transverse and longitudinal sections, if"/j (after Ulvich). 



Chasmatopora Eicliwald {Phylloporina Ulr.) (Fig. 497). Branches inegnlarly 

 anastomosing, with two to eight ranges of zocecia on the celluliferous side. Taljulated 

 interstitial spaces generally present, closed at the surface. Ordovician and Silurian. 



Pseudohornera Roemer (Drymotrypa Ulr.). Ordovician to Devonian. Chaino- 

 dictyon Foerste. Coal Measures. 



Family 2. 



Fenestellidae Kiug. 



Zoaria forming reticulate expansions, celluliferous on one side only. TJiey are com- 

 posed of rigid branches united by regular non-poriferous bars {dissepiments); or may be 

 sinuous and anastomose at regular intervals ; or may remain free. Zocecia enclosed in 

 a calcareous crust, which is minutely porous, especially on the non-cell uliferotts side. 

 Primitive portions of zooncia oblong, quadrate or hexagonal in outline. Superior hemi- 

 septum usually present, the inferior one less frequently. Primary orifice anterior, semi- 

 elliptical, trimcated behind. External apertures rounded, with peristome, and covered, 

 when perfect, by centrally perforated closures. Silurian to Permian. 



The zoarial cliaracters of the Fenestellidae are extremely constant, and are of tlie greatest 

 systematic importance. The zocecial cavity in this family is very similar to that of the 

 Ptilodictyonidae and Rhinidictyonidae ; and the same is also true of both tlie primary and 

 external orifices. 





Fic. 4i)8. 



Fencstellti retifarmisHi-hUAh. Permian Doloniitir ; Piissneck, Tlniiin-ia. .1, Fra,L;nu-nL cil' /oariuni, natural si'/e. 

 B, Portion of external surface, slightly enlarged. C, Magnilied jxirtion of interior celluliferous surface. 



