Gexeka of the Xokth American Palaeozoic Bryozoa. 527 



Akthrostylcs, Ulrich. 

 (Amer. Geologist, Yol. I, p. 230. 1888.) 

 Type, Arthrostylus tenuis, Ulrich. 



Zoarium somewhat fruticose ; composed, of numerous, slender, 

 equal segments, joined to each other by terminal articulation ; 

 celluliferous on one face only; opposite face longitudinally 

 striated; cell apertures disposed in three or more longitudinal 

 rows, separated by ridges. 



Family Stictoporidse, Ulrich, emend. 



The forms included in this family are very similar in their 

 mode of growth to Cystodictyidas, but differ from the forms in 

 that family in the absence of pseudo-septa and lunaria, the dif- 

 ference in the skeleton making a corresponding difference in the 

 living organism. The following genera are included in this 

 fajnily: Ceeamella, Edbydictta, Euspilopoea, Evactinopoba, 



PaCHYDIOTYA, PfllTLLODICTYA, PrISMOPOEA, ScALAEIPOEA, SeMIO- 



poea, Stictocella, Stiotopoea, Stictoporidra, Stictopoeella, 

 Taeniodiotya, Taeniopoba and(??) Actinoteypa. 



Ceeamella, Hall. 

 (Pal. N. T., Yol. Yl, p. xix. 1887.) 

 Type, Ceramella scidacea, Hall. 



(Plate 14, figs. 2-6.) 

 Zoarium consisting of thin, foliaceous expansions, arising from 

 a spreading base ; celluliferous on each face ; cells tubular, 

 oblique; cell apertures oval or circular, disposed in quincunx 

 order ; surface marked by sterile maculae, which are usually de- 

 pressed below the general surface of the branch. 



EuEYDicTYA, Ulrich. 

 (Geol. Sur. Ill, Yol. YIII, p. 309. 18130.) 

 T^^pe, Eurydictya montifera^ Ulrich. 



" Broad, simple or irregularly divided bifoliate expansions 

 without nonporiferous parallel margins ; surface with more or 

 less conspicuous, small, solid maculae or monticules ; zooecial 



