232 PALEONTOLOGY OF NEW YORK. 



giiished by the smaller, sub-polygonal, more closely disjiosed cell apertures, and 

 its maculjc of larger cell apertures : from F. micropora and F. segregata by the 

 much more closely disposed cell apertures, and the fewer mesopores, which 

 never entirely surround an aperture. 



Formation and locality. Hamilton group, York, Livingston county, N. Y. 



FiSTUUPORA DECIPIENS. 



PLATE LIX, FIG. ». 



Thalloatigma decipiens, Hall. Trans. Albany Institute, vol. x, p. 187. 1881. 



" " Report of State Geologrist for 1883, p. 29. 1884. 



ZoARiUM consisting of lamellate expansions, incrusting other objects, usually 

 Cyathophylloid corals. Cells tubular, cylindrical, oblique or rectangular to 

 the surface, always opening directly outward ; the septa occur more fre- 

 quently near the surface than in the lower portion of the cell tubes. Inter- 

 cellular tissue vesiculose, vesicles comparatively large, and irregularly dis- 

 posed near the base, more regularly superimposed above, but not having the 

 ajjpearance of septate tubuli, from four to six in the space of 1 mm. 

 ineiisured longitudinally. Cell apertures polygonal or sub-polygonal, diame- 

 ter from .25 to .30 mm., irregularly disposed, sometimes in contact, at other 

 times separated by nearly twice the diameter of an aperture. Peristomes 

 thin, equally elevated. Mesopores variable in form and size, sometimes 

 minute, at other times equal in diameter to the cell apertures; margins 

 of the same height and thickness as the peristomes. Surface marked by 

 broad, slightly elevated monticules, upon which the cell apertures and meso- 

 pores are of the same size as on other portions of the frond. 



When the frond is well preserved it is frequently very difficult to distinguish 

 the cell apertures from the mesopores, both being polygonal and often of the 

 same size, the surface resembling that of a Paleschara ; when the frond is 

 worn the appearance is very different, the apertures being larger, less angular, 

 more nearly circular, and much more conspicuous than the mesopores : without 

 a very careful examination, it would naturally be supposed that this appear- 

 ance of the fossil Wcas due to an extremely thin Paleschara incrusting a 

 FiSTULiPORA, some portions being worn away, showing the Fistulipora be- 



