224 PALEONTOLOGY 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 appear.ance 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. decipims, 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. viicro- 

 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. dense by the greater interval 

 between the cell appertures, and the absence of maculae compo.sed of cells larger 

 than on other portions of the frond : from F. intcrcellata 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. 



