82 PALEONTOLOGY OF NEW YORK. 



lete; posterior margin strongly elevated, slightly denticulated, projecting 

 over and partially concealing the opening. The surface contiguous to the 

 posterior margin is convex, giving to the apertures the appearance of small 

 openings in the side of a rounded elevation. Monticules destitute of cell 

 apertures, their centers distant from each other about 4 mm. Intercellular 

 space occupied by irregular vesicles or septate tubuli ; space beneath monti- 

 cules without interior structure. 



This species may be distinguished by the hemispherical monticules and the 

 sub-imbricating appearance of the cell apertures. 



Formation and locality: Upper Helderberg group, Falls of the Ohio river. 



LiCHENALIA PEBMAKGINATA. 



PLATE XXVI, FIG. -20. 



Lichenalia permarginata. Hall. Trans. Albany Institute, vol. x, abstract, p. 10. 1881. 



Report of State Geologrist for 1882. Expl. pi. 24, dg. liO. 1883. 



ZoARiUM consisting of lamellate expansions; thickness of the specimens observed 

 .50 mm. Cell apertures circular, diameter .40 mm. ; irregularly and not 

 closely disposed : peristomes strong, distinctly and equally elevated. Surface 

 marked by non-celluliferous maculae, which are distant from each other 7 

 mm. ; the apertures immediately adjacent being slightly larger than on other 

 portions of the frond. Surface where well preserved finely granulose. 



Formation and locality. Upper Helderberg group, Onondaga Valley, Onondaga 

 county, N. Y. 



PiLEOTRYPA, S. g. 



Lichenalia (Pileotrypa) pyriformis. 



PLATE XXXI, FIGS. 21-27. 



Lichenalia pyriformU, Hall. Trans. Albany Institute, vol. x, abstract, p. 12. 1881. 



(PiUotrypa) pyrifonnis. Report of State Geologist for 188.5. Expl. pi. 31, figs. 21-27. 1887. 



ZoABiUM consisting of thin lamellate expansions incrusting other objects. On the 

 thinner portions of the frond the cells are very oblique, sometimes a portion 

 of the walls being exposed for nearly the entire length, presenting a pyri- 



