Upper Helderhcrg Group, 



147 



and form, frequently hexagonal, length from equal to three times the 

 width, which is usually about .35 mm.; at the angles are frequently 

 strong obtuse spines. 

 Locality — Onondaga Vallev, N. Y. * 



Ch^TETES ? (TrEMATAPORA ?) INTERNASCEI^S, 11. Sp. 



Eamose, solid; diameter 8 mm. ; cells tubular, polygonal, arising from 

 the center of the Branch, gradually diverging till within one mm. of 

 the surface, when they turn more abruptly outward, frequently ten 

 mm. in length, nearly the entire length angular; apertures circular or 

 oval, diameter .33 mm., contiguous, oblique, subimbricating ; on one 

 side of the aperture the cell-wall projects above the surface .17 mm.; 

 maculae at irregular distances, centers noncelluliferous; tubes septate ; 

 exterior of cell-wall transversely corrugated. 



Locality — Falls of the Ohio river. 



TREMATAPORA, ffall 

 Trematopora arborea, n. sp. 



Ramose, solid; branches frequent, diameter 2.50 mm.; cells tubular, 

 polygonal; apertures oval ; cells septate; septa occurring at irregular 

 intervals; length of apertures .22 mm., width two-thirds the length, 

 usually irregularly arranged, but sometimes occurring in transverse 

 oblique rows, distance variable ; the margins of apertures and inter- 

 vening space have numerous minute spines, from six to eight, sur- 

 rounding an aperture ; no maculas. 



Locality — Falls of the Ohio river. 



TrEMATOPORA ? AXXULATA, U. Sp. 



Ramose, solid; branches occurring at intervals of from 4 to 15 mm., 

 diverging at an angle of 45°; diameter three mm.; cells tubular, reg- 

 ularly curving to the surface, diameter at aperture .25 mm., polygonal, 

 walls thin, sometimes thickening at the surface constricting the cell- 

 apertures; cells septate; septa closely arranged ; sometimes angular 

 pits occupy the intercellular space of the surface, apertures irregularly 

 arranged, with small spines at the angles, giving to the surface an acu- 

 leate appearance; at intervals of two mm. occur elongated elevations 

 at right angles to the branch, two or more elevations being on a line 

 and giving to the branch an annulatcd appearance ; a narrow space 

 along the middle of the elevations without apertures, but frequently 

 with smar. pits. This species can be easily distinguished by its strong 

 annulations. 



Locality — Falls of the Ohio river. 



