Maryland Geological Survey 253 



Description. — " Neuropteris fronde pinnata (bipinnata ?) pinnulis 

 tenuibus oppositis distantibus, sessilibus, oblongis, basi rotundatis vel 

 subcordatis, apice attenuatiS;, subobtusis ; nervo medio crassiusculo, venis 

 creberrimis tenuissimis obliquis furcatis ; rhachi gracili tereti." — Dunker, 

 1846. 



A large amount of material has been referred to this species since 

 Bunker's day, so that his diagnosis may be considerably amplified. In 

 general these forms show the following characters : 



Fronds large bipinnate or tripinnate. Eachis stout. Pinnas linear- 

 lanceolate, alternate to subopposite, becoming pinnatifid distad. Pin- 

 nules usually attached by their whole base, which is slightly expanded, 

 contiguous but usually separated to the base, lanceolate, slightly falcate, 

 acuminate. Margin usually entire, more rarely somewhat dentate in the 

 apical portion. Venation of the usual CladopJilebis type. Fertile fronds 

 have the rachis more slender than in the sterile fronds. The sori are 

 borne on a distal branch of a furcate vein as in other Potomac species 

 of OladopKlebis, and form a row on either side of the midvein of the 

 pinnules, which are othermse indistinguishable from the sterile pin- 

 nules, though inclined to be straighter. 



This species has been made to include a large amount of material 

 from various horizons and localities, which in the first instance was 

 described as various species of Neuropteris, Alethopteris, Pecopteris, 

 Pteris, etc. It is not at all certain that the result may not be a com- 

 posite species made up of several distinct species with indistinguishable 

 vegetative characters, and it would not be diflficult to select still other 

 forms from various parts of the world which could scarcely be separated 

 from the foregoing. 



CladopJilebis Albertsii was not recognized as such in Professor Fon- 

 taine's Potomac studies, but it is obvious that the forms described as 

 CladopJilebis inclinata and CladopJilebis denticulata (this was described 

 as a new species and is decidedly different from Brongniart's species of 

 the same name which JSTathorst has referred to CladopJilebis), and as 

 Aspidium angustipinnatum are identical with each other and with those 

 ferns in the European Wealden which are referred to CladopJilebis Al- 



