206 L. Lesquereux on the Coal Formations of North America. 
 Seaccatly 
(a silicate); it is more likely identical with emerald-nickel. 
mongst the omissions I notice the analyses of the meteor! 
Philadelphia, Noy. 30th, 1861. 
| 
Art. XX.—On some questions concerning the Coal Formations of 
North America. Families, Genera and Species of Coal P est 
the United States; by Leo LesquerEvx. (Continued trom 
vol. xxxii, p. 205.) 
Pecopteridece. 
The Pecopteridec have a bi- or tri-pinnatifid frond with unequth 
open pinnz and equal, oblong or linear-obtuse pinnules, gener ee 
united together near the base and thus attached to the rachis x 
the whole enlarged, sometimes decurrent, very rarely glose 
base. ‘The medial nerve is strong, straight, generally ascendi?s 
to the top of the leaflets, and the veinlets are either straight 
perpendicular to the medial nerve, simple or forking eee 
twice, or somewhat oblique, arched and dichotomous. The sal 
tification is apparently punctiform; sometimes marginal 
continuous as in the genus Preris, ‘ 
__ This definition is, with slight modification, that of Prof. oe 
niart. Though the last remark about the fructifications of 
been generally repeated by European authors, I do not know 
| we have to suppose that their fructification may be sometime 
marginal. If species of this tribe were found with evident ™™ 
