230 PALEONTOLOGY OF NEW YORK. 



mersed appearance. Mesopores very minute, generally only a single series 

 between adjjieent apertures. There are numerous, comparatively, very 

 strong conical nodes, each one occupying the place of a mesopore, and fre- 

 quently forming the most conspicuous feature of the surface. 



This species may be distinguished from F. muliaculeata by the smaller, 

 more closely and regularly disposed cell apertures ; the nodes are much 

 stronger, fewer in number, and are situated not on the peristomes, but between 

 the cell apertures, replacing a mesopore. From F. densa it may be distin- 

 guished by its smaller, less closely disposed cell apertures, less numerous and 

 much more prominent nodes, and absence of monticules on which the cell 

 apertures are larger than on other portions of the frond : from F. segregata by 

 the smaller, more oval, much more closely and regularly disposed cell apertures, 

 smaller mesopores and the prominent nodes : from F. micropora by the slightly 

 larger, more decidedly oval, and more closely disposed cell apertures, compara- 

 tively smaller mesopores and prominent nodes: from F. minuta by the smaller, 

 more decidedly oval cell apertures, smaller mesopores, and more prominent nodes, 

 which are situated between the apertures, and not on the peristomes and mar- 

 gins of mesopores as in that species : from F. involvens by the somewhat larger, 

 more oval and more closely disposed cell apertures, there being but a single 

 series of mesopores between adjacent apertures, and also by the prominent 

 nodes : from F. intercellata, of the Upper Helderberg group, by the smaller cell 

 apertures, thinner peristomes and more prominent nodes : from F. mediopora, 

 of the Lower Helderberg group, by the smaller cell apertures, much smaller 

 mesopores, and more prominent nodes : from F. parasitica, of the same geolog- 

 ical horizon, by the more closely and regularly disposed cell apertures and the 

 prominent interapertural nodes. 



Formation and locality. Hamilton group, West Hamburg, Erie county, N. Y. 



