42 AMERICAN FOSSIL BRYOZOA. [bull. 173. 



DiPLOPORARiA ( = DiPLOPORA Young and Young)/ 



Zoarium as in Pinnatopora, but ha.s no lateral l)ranchlets. 

 Genotype: Dlplop<ym marginalis Young and Young. Mississip- 

 pian, Carboniferous. Two species. 



Ramipora Toula. 



Family SPHRAGIOPORID^ Ulrich. 



Sphragiopora Ulrich. 



Zoarium parasitic, forming small, circular, subhemispheric patches 

 on foreign bodies; zocrcia of the same type as in Fenestella; apertures 

 circular, with a slight peristome, arranged in one or two rows on the 

 summits of slightly elevated, radially arranged, broad ridges; spaces 

 between raised portions solid. 



Genotype and only known species: Sj>hragioj>ora parasitica Ulrich. 



Mississippian. 



Family ARTHROSTYLID^ TJlrich. 



Zoarium articulated, consisting of numerous subcylindrical segments, 

 united into small pinnate or bushy colonies, or of continuous, dichoto- 

 mously divided branches; zooecia subtubular, more or less obliqui\ 

 radially arranged about a central axis, and opening on all sides of 

 the segments; or one side may be noncelluliferous and longitudinally 

 striated. 



Arthrostylus Ulrich (Arthronema Ulrich). 



Zoarium bushy, dichotomously branching, the whole consisting of 

 numerous exceedingly slender, equal, subquadrate segments, united 

 by terminal articulation; one face longitudinally striated, on each of 

 the other, commonly three, faces a linear series of apertures between 

 longitudinal ridges. 



Genotype: Helojjora tenuis James. Ordovician. Four species. 



IIelopora Hall. 

 Like Arthrostylus, but the segments are generally larger and have 

 zooecial apertures on all sides. 



Genotype: IIelopora fragilis BaW. Ordovician, Silurian. Twelve 



species. 



Arthroclema Billings. 



Zoarium of segments cellulif erous on all sides, articulated terminally 

 and laterally in a pinnate manner; apertures oval, in series between 

 longitudinal ridges. 



Genotype: Arthroclema pulchellum Billings. Ordovician. Six 



species. 



'Diploporaria proposed for Diplopora, preoccupied by Schafhautl. 



