224 
PALAEONTOLOGY OF NEW YORK. 
preserved having several nodes or short spinules. Mesopores usually minute, 
but sometimes equal in size to the cell apertures; margins elevated equally 
with the peristomes, and when well-preserved having minute nodes at the 
angles. Surface marked by low, rounded monticules, the centers of which 
are distant from each other about 4 mm., occupied by apertures and 
mesopores of the same size as those on other portions of the frond. 
The surface of the frond presents a varying appearance according to the 
condition of preservation ; when perfectly preserved the margins of the 
mesopores are elevated equally with the peristomes; the apertures and 
mesopores being so disposed as to give a striated appearance to the surface, 
and it is often difficult to distinguish the cell apertures from the mesopores; 
when the surface is worn or macerated the striated appearance is obscure or 
obsolete, and the cell apertures are very conspicuous, frequently somewhat 
obscurely disposed in quincunx order; in this condition of the frond the 
apertures frequently appear much larger than when perfectly preserved. 
This species most nearly resembles F. decipiens, but may be distinguished by the 
smaller and more nearly oval cell apertures, and their disposition,which in connec¬ 
tion with the mesopores, gives a striated appearance to the surface; the smaller 
mesopores, the smaller and more closely disposed monticules, and the uniform 
size of the cell apertures: when macerated it resembles F. segregata, but the 
cell apertures are smaller, more closely and regularly disposed : from F. micro- 
pora it is distinguished by the larger cell apertures and mesopores, and the 
coarser appearance of the frond : from F. multaculeata by the smaller and more 
broadly oval cell apertures, and the absence of prominent spinules on the peri¬ 
stomes and angles of the mesopores: from F. dmsa by the greater interval 
between the cell appertures, and the absence of maculae composed of cells larger 
than on other portions of the frond: from F. intercellata. of the Upper Helderberg 
group, it may be distinguished by the thinner and more elevated peristomes, 
the greater interval between the cell apertures, and the much larger mesopores : 
from F. digitata by the manner of growth, the greater interval between the cell 
apertures, and the absence of prominent nodes between the apertures. 
Formation and locality. Hamilton group, Erie county, and at Delphi, N. Y. 
