l 



342 MOLLUSCOIDEA— BRYOZOA phylüm v 



sisting of anastomosing branches, which form a regulär, roimd-meshed network. 

 Zooccia in two or more rows. Devonian to Permian. 



Ptüoporella, Ptüoporina Hall. Siliirian and Devonian. Eeteporina d'Orb. 

 Devonian and Lower Carboniferous. Anastomopora Simpson. Devonian. 



Family 3. Acanthocladiidae Zittel. 



Zoaria poriferous on one side only, pinnate or forminy fenestrated expansions ; con- 

 sisting of sträng, central stems which give off numerous, smaller, lateral hranches fr am 

 their opposite margins. The lateral hranches are free or unite with those of the next 

 stem. Non-poriferous dissepiments ahsent Zooßcial characters mostly as in the Fene- 

 stellidae. Silurian to Permian. 



Pinnatopora Vine. {Glauconome auct., non Goldfuss) (Fig. 500, b, c). Zoaria 



small, delicate, with short, free, lateral 



^ FSW^ branches given off frequently at regulär 



Aji '-.\ ,, ^A^*i^r intervals. Cells in two rows, one on 



<^''^ M-'r >'-,''- Z ' ^*^ ^^^^ ^^^^ ^^ ^ moderate median keel. 



pp'^ Silurian to Permian. 



/^^•|^p.....l Septopora Vroiit. Zoaria fenestrated, 



-i ^(^lM yr\ flabellate or leaf-like. Primary branches 



^ t> \^^^ numerous, increasiug by bifurcation or 



j ' :^\^ j^.^ ^ f Interpolation ; the lateral branches 



^^^p^ ^ M/Q uniting with those of adjacent stems. 



^^^^ rj.'^m^ Reverse usually with fine Striae and 



^ %ti„-»r scattered dimorphic pores. Celluliferous 



Fig. 500. side with two rows of zooecia arranged 



a, Acanthociadia fruticosa uir. i/i. I&, Pinnatopora as in Pinnatopora. Chester Group and 



tenuiramosa Ulr. V^. c, P. vinei Ulr. i/i and 9/i (after q^^^ Measures. 



Acanthociadia King (Fig. 500, a). 

 Like Pinnatopora, but larger, stronger, and with three or more ranges of cells. Goal 

 Measures and Permian. 



Synocladia King. Differs from Septopora in the same manner as the preceding 

 differs from Pinnatopora. Permian. 



Ptilopora M'Coy {Dendricopora Koninck). Zoaria pinnate, the central brauch 

 much stronger than the oblique lateral branches, which are united by dissepiments. 

 Zooecia in two ranges. Devonian and Lower Carboniferous. 



Diploporaria N. and B. {Diplopora Young). Essentially a Pinnatopora without 

 lateral branchlets. Garboniferous. 



Family 4. Arthrostylidae Ulrich. 



Zoaria articulated, consisting of numerous suh-cylindrical segments united into small 

 pinnate or bushy colonies, or of continuous, dichotomously divided hranches. Zooecia suh- 

 tuhular, more or less oblique, radially arranged ahout a central axis, and opening on all 

 sides of the segments ; or one side may he non-celluliferous and longitudinally striated. 

 Ordovician and Silurian. 



Arthrostylus Ulr. (Fig. 501, d, e). Zooecia bushy, dichotomously branching, the 

 whole consisting of numerous exceedingly slender, equal, subquadrate segments, 

 united by terminal articulation. Zooecia usually arranged in three rows between 

 longitudinal ridges ; the fourth face with lougitudinal Striae only. Ordovician. 



Helopora Hall (Figs. 501,/; 502). Like the precediug, but the segments are 

 larger, and have zooecial apertures on all sides. Ordovician and Silurian. 



