346 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Phyllodictya Ulr. ZocEcial tubes long, with complete cliaphragm.s, Imt no 

 lieniisepta. Ordovician. 



Pachydictya (Fig. 506), Trigonodictya Ulr. Ordovician and 

 Silurian. 



Family 9. Oystodictyonidae Ulricli. 



Zoaria consisting of two or three layers of cells grown together 

 hack to bach, forming branching, perforated or entire leaf -like ex- 

 pansions, or triangular branches. Primitive cells semi-cordate or 

 obovate-acuminate in outline, arranged longitudinally. Primitive 

 afcrture sub-circular, but becoming drawn out into a, tubular 

 vestibule as groivth proceeds. Superficial aperture with peristome, 

 and more or less well - developed hinaritim. Interzooscial spaces 

 occupied, by vesicular tissue, often filled, with a calcareous deposit 

 near the surface. Silurian to Permian. 



Fig. 506. 



Pachydictya foliata 

 Ulr. Black River; Min- 

 nesota. Tangential sec- 

 tion, 14/j (after Ulrich). 



Gystodictya Ulr. (Arcanopora Vine ; Stictocella Simpson) (Fig. 505, (7, e). Zoaria 

 ramose, brandies sharply elliptical, with sub-parallel, non-poriferous margins. Intei'- 

 apertural space finely striated, granulose or smooth ; pits and cells showing (uily in 

 a worn condition. Silurian to Permian. 



Coscinium Keyserling {Goscinotrypa Hall) ; Dichotrypa Ulr. Silurian to Permian. 



Taeniopora Nich. {Pteropora Hall ; Btictoporidra Simpson). Distinguished from 

 Gystodictya by having a longitudinal ridge or keel, which divides each face into two 

 equal parts. Devonian. 



Thamnotrypa, Semiopora, Acrogenia, Geramella, Phractopora, Prismopora, Scalaripora 

 Hall ; Goniocladia Etheridge ; Ptilocella Simpson. Devonian and Lower Carboniferous. 



Evactinopora Meek and Worth. (Fig. 507, b, c). Zoaria free, consisting of four or 

 more vertical leaves arranged in a stellate or cruciform fashion. Lower CarboniferoiLS. 



Fic. 507. 



a, Glyptopora sagenella-lata Ulr. l/j. 6, Evactinopora quinque radiafa Ulr. Vi- 



Meek and Wortlien i/j (after Ulrich). 



c, d, E. radiata 



Glyptopora Ulr. (Fig. 507, a). Zoaria consisting of thin expansions traversed on 

 both surfaces by salient ridges, or of uni-laminate bases on which the coalescing ridges 

 of the upper surface are greatly developed and fornx large leaves. These lidges or 



