Genera of the Xoeth American Palaeozoic Bryozoa. 563 



Family Ceramoporidae, Ulrich. 

 • The forms in this family are usually incrustiDg lamellate 

 expansions, but sometimes free; cell apertures arched or triangu- 

 lar, usually imbricating; no pseudosepta. 



The following genera are included in the family : Atactopoba, 

 Ceramopoba and Petigopoba. 



Atactopoba, Ulrich. 



(Jour. Cin. Soc. :N'at. Hist., A^ol. II, p. 119. 1879.) 



Type, Atactopora hirsuta, Ulrich. 



"Zoarium consisting of very thin expansions incrusting other 

 objects ; cell tubes short, very oblique, frequently alternating 

 and imbricating ; cell apertures oblique to the surface, oval but 

 appearing petaloid from the numerous nodes, which occur not 

 only between the apertures, but also on the cell walls near the 

 aperture ; surface with numerous small monticules, the centers of 

 which are destitute of cell apertures." 



Ceramopora, Hall. 

 (Pal. N. Y., Yol. II, p. 16-^. 1852.) 



Type, Ceramopora imhricata^ Hall. 



(Plate 20, figs. 10-15.) 



Zoarium consisting of flattened discoidal or lamellate incrust- 

 ing expansions ; cells radiating from one or more centers ; cell 

 apertures arched or triangular, frequently alternating and imbri- 

 cating ; mesopores few or entirely wanting ; interapertural sur- 

 face solid. 



Petigopoba, Ulrich. 



(Jour. Cin. Soc. Nat. Hist., Yol. Y, p. 155. 1882.) 



T^^pe, Petigopora gregaria, Ulrich. 



Zoarium consisting of small circular or lamellate expansions 

 incrusting other objects ; cell tubes rectangular or oblique to 

 the surface ; walls very thin ; cell apertures oval or circular, 



