266 PALEONTOLOGY OF NEW YORK. 



apertures circular or very broadly oval, diameter .35 mm. ; irregularly and 

 very closely disposed, usually very nearly or quite in contact. Peristomes 

 strong, generally equally elevated, but sometimes the posterior portion is the 



more prominent. 



********* 



Formation and locality. Hamilton group, near Leonardsville, Madison county. 

 New York. 



Pbismopora lata. 



NOT KIGURBD. 



ZoARiDM consisting of a dichotomously branched frond, arising from a spread- 

 ing base attached to foreign bodies ; branches triangular, two of the sides 

 of equal width, the third wider ; on the specimens observed the two equal 

 faces of a branch have a width of 6 mm. each, the other 9 mm. ; the other 

 branches of the same frond are somewhat smaller; margins of each face 

 essentially parallel, the branches scarcely increasing in size before bifur- 

 cation : non-celluliferous marginal space comparatively broad, width nearly 

 .75 mm. ; there are also, at more or less regular intervals along the margin, 

 obtusely triangular areas, destitute of cell apertures, having a width of about 

 3.50 mm., and a depth of nearly 2 mm. ; sometimes these areas are con- 

 tinuous ; bifurcations comparatively infrequent on the specimens observed, 

 occurring at intervals of .20 mm. or more ; branches diverging at an angle of 

 about sixty degrees. Cells tubular, cylindrical, arising from mesial laminae, 

 which radiate from the center to each angle of the branch. Along the 

 middle of the branch the cells have a direction parallel with the axis, becom- 

 ing more and more oblique as they recede until the marginal cells are some- 

 times nearly rectangular to the axis ; septa very infrequent or obsolete. 

 Intercellular tissue vesiculose ; vesicles more compactly disposed near the 

 surface than at the center of the branch. Cell apertures trilobate, pustuli- 

 form, length about .20 mm., width from one-half to two-thirds the length ; 

 near the middle of a face of the branch they are disposed in somewhat 

 irregular, longitudinal rows, but over the greater portion of the face in more 

 or less regular, oblique, ascending rows, which are distant nearly twice the 



