40 AMERICAN FOSSIL BRYOZOA. [bull. 173. 



Thamniscus King. 



Zoarium as in Polypora, but branches bifurcate more f requenth' and 

 are rarely or not at all connected by dissepiments. 



Genotype: Ceratophytes duhius Schlotheim. Range, Silurian-Car- 

 boniferous. Thirteen species. 



Phyllopora King. 



Zoarium funnel-shaped, celluliferous on the outer face; fenestrules 

 oval, branches anastomosing or connected by broad celluliferous dis- 

 sepiments; zooecia in two ranges normally; without median keel. 



Genotype: Gorgonia ehrenbergi Geinitz. Devonian. One species. 



Reteporidra (=Reteporella Simpson)^ (Anastomopora Simpson). 



Zoarium a flabellate or undulating expansion with thickened mar- 

 gins; branches sinuous or zigzag, anastomosing at short and regular 

 intervals so as to produce a regular series of oval fenestrules; aper- 

 tures in three to seven rows; branches without a median carina. 



Genotype: Retepora undulata Sm\]iiion = FenesteUa perundata Hall. 

 Devonian. Three species. 



Reteporina D'Orbigny. 



Zoarium as in Reteporidra, but the zooecia are in two ranges, with the 

 apertures separated or not by a more or less well-marked median 

 carina. 



Genot3''pe: Retepora j>r/«(?(2 Goldfuss. Devonian, Mississippian. 

 Eight species. 



Ptiloporella Hall (Pinnaporella Simpson, 1897). 



Zoarium a fenestrated funnel-shaped expansion; branches of two 

 sizes, the smaller or secondary branches proceeding laterally from the 

 larger or primary ones, either from one or both sides; as the frond 

 expands, other large branches proceed from the primary ones, this 

 process continuing during the growth of the frond; apertures in two 

 rows separated by a carina; the carinse of the primary branches more 

 prominent than those of the secondary branches. 



Genotype: FenesteUa {Ptiloporella) laticrescens Hall. Silurian, 

 Devonian. Four species. 



Ptiloporina Hall (Pinnaporella Simpson, 1895, Pinnaporina 



Simpson). 



Zoarium like that of Ptiloporella in mode of growth, but branches 

 have three or more rows of apertures and no median carina. 



Genotype: Fenestella {Ptiloporina) conica Hall. Devonian. Four 

 species. 



'Beteporidra is proposed for Reteporella, preoccupied by Busk, Challenger Report, X, 1884, p. 126. 



