288 PALEONTOLOGY OF NEW YORK. 



Prismopora sparsipora. 



PLATE XXXII, FIGS. 2t-«8. 



Thalloftiff'nn sjMrsipora, Hall. Trans. Albany Institute, vol. x, abstract, p. 13. 1881. 

 Pri»mi>pora " " Report of State Geologrist for 1885, advance sheets. PI. 32, figs. 25-28. 



1886. 



ZoARiUM consisting of triangular, bifurcating branches, sides concave, two of 

 them equal in length, the third a little wider. Cell apertures minute, oval 

 or obscurely trilobate, arranged in oblique, ascending rows, from the middle 

 of each face, comparatively infrequent ; the apertures at the middle of the 

 branch are the smallest, having a length of about . 1 8 mm., gradually growing 

 larger to the margin, where they have a length of from .22 to .25 mm., and 

 are frequently pustuliform. Peristomes strong, equally elevated, and with two 

 slight denticulations on the posterior portion. Surface flat, finely granulose. 



All the specimens observed are flattened, and in this condition have very 

 much the appearance of Lichenalia. It may be distinguished from P. subcon- 

 cava and P. triquetra by its wider branches and more distant apertures ; from 

 P. paudrama by its smaller and more infrequent cell apertures ; from P. lata by 

 its narrower branches, smaller and more infrequent cell apertures. 



Formatim and locality. Upper Helderberg group. Falls of the Ohio river. 



