202 PALEONTOLOGY OF NEW YORK. 



LiCHENALIA CULTELLATA. 



PLATE LXIV, FIGS. 1, 2. 



Liehentdia eultdlata. Hall. Report of State Geologist for 1883, p. 35. 1884. 



ZoARiUM consisting of explanate fronds, free or incrusting other objects, thick- 

 ness usually about 1 mm. No masses formed by the superimposition of 

 successive layers of growth have been observed. Cells tubular, cylindrical 

 rectangular or oblique to the surface, non-septate, walls very thin. Inter- 

 cellular space vesiculose, vesicles comparatively very large, usually irregu- 

 larly disposed, sometimes more irregularly superimposed, but in the speci- 

 mens observed, never appearing as walled, septate tubuli. Cell apertures 

 trilobate or trifoliate, the posterior lobe or fold is remarkably well devel- 

 oped, being much larger than the other two combined, length .30 mm., 

 width three-fourths the length, radiating from the center of the monticules, 

 forming irregular, intersecting rows. Peristomes thin, posterior portion the 

 more strongly elevated and with two moderately prominent denticulations. 

 Interapertural space flat, smooth. Surfaqe marked by strongly elevated, 

 obtusely conical monticules, the centers of which are distant about 5 mm., 

 irregularly disposed ; on one side of the monticule, commencing at the 

 center and extending to the base, there is a narrow, gradually enlarging 

 depression ; the apertures nearest the center are slightly larger than the 

 others, and extending from the center of the monticules to these apertures 

 there are sharply angular, gradually enlarging, prominent ridges ; this feature 

 gives to the cell the appearance of being so oblique that the upper portions 

 of their walls are exposed for the entire length, but a section shows that 

 they are only slightly oblique. In a transverse section the trilobate form 

 of the cells is more conspicuous ; the interapertural vesicles vary greatly in 

 size and are frequently larger than the cell apertures. 



The cell apertures of the specimen from which fig. 1, pi. 64, was made do 

 not show the usual trilobate form. 



The strong monticules and prominent ridges extending from their centers 

 to the adjacent apertures are features which distinguish this species from any 



