32 AMEBIC AN FOSSIL BRYOZOA. [bull. 173. 



Orbipora Eicliwald (Orbitulites Eichwald). 



Family BATOSTOMELLID^ Ulrich. 



Zoariiim usually ramose; zooeciawith thick walls in the mature region, 

 appearing here to be fused; diaphragms in the peripheral region often 

 centrally perforated; acanthopores and mesopores usually present, the 

 latter small and sometimes monilif orm in shape. 



Batostomella Ulrich (Geinitzella Waagen and Wentzel). 



Zoarium ramose, branches slender; zooecia with few diaphragms; 

 apertures of zooecia small, circular or oval; interspaces rounded or 

 canaliculate, spinvilose, the acanthopores small and usually very nu- 

 merous; mesopores small, with subcircular openings. 



Genotype: Batostomella spinulosa Ulrich. Range, Silurian-Per- 

 mian. Six species. 



Bythopoea Miller and Dyer. 



Zoarium ramose, branches usually slender, sometimes of considerable 

 size; zooecia practically without diaphragms; apertures oblique, nar- 

 rowing above; interspaces canaliculate; mesopores few; acanthopores 

 comparatively strong, rarely more than one to each zooecium, some- 

 times wanting. 



Genotype: Bythoporafruticosa Miller and DjQY—ITelopora dendHna 

 James. Range, Ordovician-Devonian. Ten described and five new 

 species, 



Callotrypa Hall. 



Zoarium ramose; apertures oval, with equally elevated peristomes 

 and with no definite arrangement; interspaces showing the openings 

 of the numerous mesopores by which the zooecia are surrounded; 

 acanthopores present. 



Genotype: Callopora macropora Hall. Silurian, Devonian. Ten 

 species. 



Trematella Hall. 



Zoarium ramose; more or less conspicuously annulated; zooecia 

 oblique, with a few diaphragms and walls much thickened in the 

 mature region; apertures arranged in a somewhat quincunx oi'der, 

 interspaces ridged, forming polygonal areas; acanthopores sometimes 

 present. 



Genotype: Trematopora anmdata Hall. Devonian. Five species. 



Eridotryfa Ulrich. 



Zoarium ramose, branches slender; zooecia more or less oblique, thick- 

 walled, and intersected by diaphragms, which are most numerous and 



