36 AMERICAN FOSSIL BRYOZOA. [bull. 173. 



MoNOTRTPA Nicholson (Ptychoneiha Hall and Simpson). 



Zoarium mass}^ hemispherical, subglobose, or discoidal; zooecia not 

 distinguishable into mature and immature regions, comparatively 

 large, prismatic, with walls thin throughout and often crinkled; dia- 

 phragms remote; neither mesopores nor acanthopores. 



Genotype: Chcetetes tindmlatus Nicholson. Ordovician, Silurian. 

 Fourteen described and two new species. 



DiPLOTRYPA Nicholson (emend. Ulrich). 



Zoarium hemispheric, discoid, globular, or irregularly massy, gen- 

 erally free; zooecia comparatively large, prismatic, with diaphragms; 

 mesopores few to many, varying in size. 



Genotype: Favosites petropolitanus Pander. Ordovician, Silurian. 

 Four described and two new species. 



Family CALLOPOEIDiE TTlrich. 



Zoarium ramose, subfrondescent, or discoidal; zooecia increasing in 

 size very gradually, their proximal portion very much like mesopores; 

 apertures subcircular, the openings of a greater or less number of 

 mesopores interspersed among them, or polygonal, in which case the 

 mesopores are few or wanting; no acanthopores. 



Callopora Hall (emend. Ulrich). 



Zoarium usually ramose, the branches frequently anastomosing and 

 forming bushy clumps; zooecia at first prismatic, four to eight sided, 

 gradually becoming cylindrical in most cases; at first with closely set 

 diaphragms, then diaphragms more distant, finally in the mature 

 region diaphragms usualh^ closely set; apertures closed at times by 

 perforated, often ornamented covers; mesopores more or less numer- 

 ous, angular, cro ,vded with diaphragms. 



Genotype: Callopora eleg a ntula'RalL Ordovician, Silurian. Twenty- 

 three described and ten new species. 



Calloporella Ulrich. 



Zoarium a thin expansion, free or incrusting; surface smooth or 

 undulated; zooecia cylindrical, with thick walls and numerous dia- 

 phragms; apertures circular, arranged in regular intersecting series; 

 mesopores numerous, angular, surrounding the zooecia in one or two 

 series; acanthopores small and few. 



Genotype : Calloporella harrisi Ulrich = MonticuUpora {Ileterotrypa) 

 circularis James. Ordovician. Three species. 



Suborder OEYPTOSTOMATA Vine. 



Zooecia short, pyriform to oblong, quadrate or hexagonal, some- 

 times tubular; orifice anterior, usually circular; the upper or front 



