340 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Family 1. Phylloporinidae Ulrich. 



Zoaria branching, celluliferous on one side only, the other side striated ; hranches 

 free or anastomosing. Zocßcia more or less tubulär, often with diaphragms. Hemisepfä 

 wanting.' Ordovician to Goal Measures. 



a, h, Chasinatopora suhlaxa (Ulr.). ö/j. 



Fio, 497. 

 (', d, Traiisvers'e aiid longitudiiial sections, i^/^ (after Ulrich). 



Ghasmatopora Eicliwald {Phylloporina Ulr.) (Fig. 497). Brauches irregularly 

 anastomosing, with two to eight ranges of zooecia on the celluliferous side. Tabulated 

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



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

 dictyon Foerste. Goal Measures. 



Family 2. Fenestellidae King. 



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

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

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

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

 Primitive porlions of zocecia oblong, quadrate or hexagonal in outline. Superior hemi- 

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

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

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



The zoarial characters of the Fenestellidae are extremely constaiit, and are of the greatest 

 systematic importance. The zooecial cavity in this faniily is very siniilar to that of the 

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

 external orifices. 





Fic. 498. 



Fenestrlld /r///u;-//(/s Scliloth. Permian Dolomite ; Pcissniick, Tlinrinj;ia. .1, Fra-inciiL of/oarium, natural size. 



Ji, Portion Ol' external surface, sH^'htly enlarged. C, Magnilied iK)rtion of iiiterioi' (teüuliferous surface. 



