276 Systematic Paleoxtology 



curved diaphragms are developed, several of the tubes, however, showing 

 3 or 4 very thin diaphragms in each, scarcely a half -tube diameter apart. 



This abundant species is difficult to classify. The writers are thor- 

 oughly satisfied that it has no close relations to any of the known 

 Ordovician genera, and equally well convinced that its natural affinities 

 are with Stenopora and allied genera. Still it can find no permanent 

 place in that genus, but will doubtless go with several other Silurian 

 and Devonian species which will eventually be grouped together as a new 

 genus. Specifically S. ? incrustans is clearly distinct, and there is no 

 associated species with which any careful observer could possibly con- 

 found it. 



Occurrence. — Helderberg Formatiox, Keyser MejMBEr. Cash 

 Valley, Pinto. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Diplostenopora n. gen. 



This new genus is instituted for a very abundant and characteristic 

 bryozoan of the Keyser limestone which agrees with Stenopora in the 

 tabulation of its zooecia but differs in being bifoliate and in lacking the 

 characteristic j^eriodic swelling of the zooecial walls. Externally it re- 

 sembles members of the Crj^ptostomata, but thin sections show it to have 

 indubitable affinities with the Trepostomatous family Batostomellidae. 

 The following diagnosis gives the supposed generic characters. 



Zoariuni of comparatively narrow, bifoliate branches with the two 

 layers of zooecia arising from a distinct mesial lamina which is duplex 

 as usual. Zooecia angular, thick walled, with rounded apertures set in 

 areas sloping inward from the sharp crest of the walls. Wall structure as 

 in Stenopora, amalgamated. Mesopores few, acanthopores small and few. 

 Diaphragms centrally perforated. Zooecial walls merely thickened in the 

 peripheral zone, but not " beaded " as in Stenopora. 



Type Escharopora siluriana Weller. 



In its general aspect and structure the type suggests Petalotrypa 

 to which the M-riters were at first inclined to refer it. However, on closer 

 investigation by means of thin sections, it proved that the noted re- 

 semblance was merely fortuitous and superficial and not truly genetic. 



