Upper Helderherg Group. 



159 



each face ; cells arising from internal plates, which radiate from the 

 center and extend to each angle ; apertures regularly or irregularly 

 arranged. 



Ptiismopora triquetra, n. sp. 

 Consisting of an irregular group of branches, diverging at an angle 

 of from forty-five to ninety degrees ; sides subangular at the middle; 

 angles at margins sharp, width of each face, 3.50 mm. ; frequently a 

 branch trifurcates; a nou-celluliferous space, at the margins of each 

 side, of about .65 mm. in width; cell-apertures circular or oval, some- 

 times subtriangular ; diameter ,25 mm.; variable, sometimes opening 

 directly outward, at other times so oblique that the upper portion 

 of the cell wall is exposed for nearly two-thirds its entire length; 

 those nearest non-celluliferous margin larger than the otliers (all inter- 

 mediate forms occurring) ; at the middle of the branch are from one 

 to three longitudinal ranges of apertures; the remaining apertures 

 more or less distinctly radiate from the center of the branch ; rows of 

 apertures frequently separated by a ridge. 



Locality — Falls of the Ohio river. 



Prismopora pauctraha, n. .<?;?. 

 Branches comparatively infrequent ; two of the sides are equal in 

 width, the remaining one wider; the equal sides are )^.75 mm. wide, 

 the third four mm.; branches occurring at intervals of twenty mm. or 

 more ; non-celluliferous space at the margin, .6G mm. wide ; apertures 

 circular, diameter .25 mm., arranged in longitudinal rows, and more 

 distinctly in transversely oblique rows ; the apertures are smallest at 

 the middle of the branch, gradually growing larger to the marginal 

 space ; intercellular tissue vesiculose. 



Locality — Thompson's Lake, Albany county, X. Y. 



SCALAKIPORA, nov. gen. 



Bryozoum consisting of irregular groups of triangular branches, 

 more or less concave, traversed transversely by sharp, elevated laminje, 

 situated at regular distances apart; branches celluliferous on each face; 

 cells arising from internal plates, radiating from the center to each 

 angle of branch ; margins and summit of laminse uon-celluliferous. 



Scalaripora scalariformis, n. sp. 

 Branches frequent, sides very concave, angles acute, width of each 

 sid^ to four mm. : summits of transverse laminae essentially straight, 

 height at the miii'He of the branch, one mm., thickness at base, .25 

 mm., distant J. 50 ram., width of non-celluliferous marginal space .48 



