22 AMERICAN FOSSIL BRYOZOA. [bull. 173. 



Family ENTALOPHORIDiE Reuss. 



Zoarium ramose, branches free, subcylindrical, with rounded and 

 more or less prominently exserted zooecial apertures opening on all sides 

 of the branches. 



MiTOCLEMA Ulrich. 



Zoarium ramose, cylindrical, consisting of long tubular zooecia, 

 which arc thin-walled and prismatic in the axial region, diverge gradu- 

 ally from the center, and bend abruptly outward near the surface, 

 often becoming free and much exserted; apertures terminal, circular, 

 usually arranged in regular transverse or subspiral series. 



Genotype: Mitoclema einctosurn Ulrich. Ordovician. Two de- 

 scribed and one new species. 



Clonopora Hall. 



Zoarium ramose; branches cylindrical, consisting of elongate tubu- 

 lar zocecia, cohering for part of their length, then bending outward 

 and becoming free; apertures terminal, not contracted, arranged in 

 rings or spirally around the branch. 



Genotype: Clmwpora semireducta ^q\\. Devonian. Three species. 



DiPLOCLEMA Ulrich. 



Zoarium dendroid, branches slightly compressed, spreading in the 

 same plane; zooecia tubular, diverging from a wavy mesial mesotheca; 

 apertures circular; prominent. 



Genotype: DlploGletiia trentonense Ulrich. Ordovician, Silurian. 

 Two species. 



Cystopora Hall. 



Zoarium cylindrical, consisting of tubular, ampullate zooecia, coher- 

 ing for the greater part of their length; distall}^ the zooecia bend out- 

 ward, becoming free and much contracted; apertures terminal. 



Genotype and only known species: Cystopora genioulata Hall. 

 Devonian. 



Family PHACELOPORID^ Ulrich. 

 Phacelopora Ulrich. 



Zoarium articulated; zooecia conical, two or more aggregated to 

 form cone-shaped bundles; apertures subterminal, circular, and 

 slightly contracted. 



Genotype and only described valid species: Phacelopora pertenuis 

 Ulrich. Ordovician. One new species in the Clinton group. 



