210 L. Lesquereux on the Coal Formations of North America. 
rescens, or at least are considered as such by some authors. To 
this section, I would still add: Pecopteris longifolia Brgt. and its 
4% Be! 
§ 2. Dicrophlebis : containing species with twice or thrice — 
veins. Our American species agreeing with it are: pe : 
oreopteridis , P. penneformis Bret., P. plumosa Brgt., (ident 
To the third subgenus Cladophlebis Brgt., with pinnules some 
times free at the base, nervules more oblique on the medial nervé, 
more divided, generally arched and dichotomons, we could rele 
as species from our coal-measures : Pecopteris Cistit Brgt., P. poly 
m Brgt., P. distans Lsqx., P. Sheafferi Lsqx., and perhaps 
P. velutina Lsqx., whose nervation is entirely obsolete and 
unknown. : 
A number of species of Pecopteridee, especially belonging 
our coal-measures, should, I think, from their peculiar appe 
ance, be grouped together in a separate genus. They are 
thick-leaved ferns, and their pinnules though mostly entire have 
a tendency to become irregularly lobed, when they increase 1D 
size, especially the lower and inferior one of each pinnz. 47° 
pinnules are unequal in size and varied in form. ‘They have® 
strong medial nerve, dichotomous or forking in ascending, 8° 
erally straight and the secondary nerves or veins diverging 
an acute angle and once or twice forked, according to the a 
of the pinnules. In this group, I would place Pecopteris nerv0s 
Brgt., P. muricata Brgt., P. Pluckneti Brgt., P. Loschii Brgt., 0% 
monly found both in the European and the American coal-meas 
ures, with the following species belonging exclusively to US: 
Sillimani Brgt., P. callosa Lsqx., (Ill. Geol. Rept: ined. 
6 3, fig. 1,) nearly related to P. Loschii, Sphenopteris ( cua 
ewb., scarcely distinguishable from P. Sillimani, and likely ® 
variety of the same, Sphenopteris Newberrit +) aD ps eget 
dimorphaLsqx. This last species is related to Pecopteris bifuret 
Sternb., referred by Prof. Geinitz to P. Pluckneti, The nerv® 
generally free at the base are sometimes distant and have a differ 
ent form.on each side of the pinnz. The upper ones are shor 
broader, broadly obtuse at the top, variously and irregularly lo 
