20 PALEONTOLOGY OF NEW YORK. 



tiulinal striae crnised by the recumbent portion of the cells. Cells tubular, 

 Kub-cylindrical, arising from the epitheca and for about one-half their length 

 parallel with it, then abruptly turning outward and opening obliquely to the 

 surface. Apertures oval, length .25 nun., width slightly less ; more or less 

 regularly alternating and imbricating. Posterior margin strongly elevated, 

 projecting over and concealing a portion of the opening ; sometimes with 

 two minute denticulations. 



There are frequent maculae destitute of cell apertures; the apertures 

 imuiediately adjacent to these being larger than the others and radiating 

 from the maculae. 



This is a very common species and can be easily recognized by the strong 

 projecting lip of the cell apertures, the prominent maculae and the arrangement 

 of the cells. 



Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 



DiAMESOPORA DISPERSA. 



PLATE X, FIGS. 20, 21. 



Tmnatrrpora tiixperxn, Haix. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 150. 1879. 



Report of State Geologist for 1882. Expl. pi. 10, figs. 20, 21. 1883. 



ZoARiUM ramose; branches hollow, diameter 3 mm. Thickness of the bryo- 

 zoum .75 mm. Inner surface covered by a transversely wrinkled epitheca. 

 Cells tubular, opening slightly oblique to the surface. Apertures circular or 

 oval, diameter .30 mm., irregularly disposed, sometimes forming transverse 

 rows : margins thick, distinctly and sometimes, equally elevated ; at other 

 times the lower portion is the more strongly elevated, giving to the aperture 

 a sub-triangular appearance. 



There are occasional maculae destitute of cell apertures, the cells, imme- 

 diately adjacent, radiating from them. 



This species differs from D. constricta in the cell apertures being less oblique 

 and more irregularly arranged. 



Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 



