346 



MOLLUSCOIDEA— BRYOZÖA 



PHYLUM V 



Phyllodictya Ulr. Zoa3cial tubes long, with complete diaphragms, biit no 

 hemisepta. Ordovician. 

 W^ß^Jl^'^J. PcLchydidya (Fig. 506), Trigonodictya Ulr. Ordovician and 



Siliirian. 



Family 9. Oystodictyonidae Ulrich. 



Fig. 506. 

 Pachydictya foliata 



Zoaria consisting of two or three layers of cells grown together 

 hack to hack, forming hranching, perforated or entire leaf-like ex- 

 pansions, or triangulär hranches. Primitive cells semi-cordate or 

 ohovate-acuminate in outline, arranged longitudinally. Primitive 

 aperture suh-circular, hut hecoming draivn out into a tuhular 

 vestihule as growth proceeds. Superficial aperture ivith peristome, 

 and more or less ivell-developed lunarium. Interzooecial Spaces 



^esota ^'^^ n^entiai^ec' ^^^^P'^*^^ ^V vesicular tissue, often filled with a calcareous deposit 



tion, i4/i (after Ulrich), near the surface. Silurian to Permian. 



Cystodictya Ulr. {Arcanopora Vine ; Stictocella Simpson) (Fig. 505, d, e). Zoaria 

 ramose, branches sharply elliptical, with siib-parallel, non-poriferoiis margins. Inter- 

 apertural space finely striated, granulöse or smooth ; pits and cells showing only in 

 a worn condition. Silurian to Permian. 



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



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

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

 equal parts. Devonian. 



Thamnotrypa, Semiopora, Äcrogenia, Geramella, Phractopora, Prismopora, Scalaripora 

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



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

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



Fig. 507. 



a, Glyptopora sagenella-lata Ulr. i/^. b, Evactinopora quinque radiata Ulr. i/j. c, d, E. radiata 

 Meek and Worthen i/i (after Ulrich). 



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 form large leaves. These ridges or 



