FOSSIL PLANTS. 441 



specimens found at Colchester, in the roof shales of coal No. 3, 

 the species has been more satisfactorily studied. Frond appa- 

 rently very large, and at least bipinnate ; secondary pinnae 

 lanceolate, with a broad canaliculate rachis; pinnules alternate, 

 oblique, obovate or oblong, nearly contiguous, slightly decur- 

 rent by the base, and united together with a slightly obtuse 

 sinus; medial nerve broad and flat, abruptly disappearing above 

 the middle of the leaflets; veins obliquely arched, slender, 

 close, mostly twice forked. 



Genus Pecopteris, Brgt. Frond bi or tripinnate, or many 

 times pinnately divided; pinnules ordinarily enlarged, united 

 together or decurrent at the base; veins oblique on the medial 

 well marked nerve, simple or forking; fruit dots round, ordi- 

 narily two ranked. The genus Pecopteris may be, and has 

 already been, subdivided, but this separation is based on such 

 variable or indistinct characters (the fructification) that it is 

 scarcely possible to attempt it, or to admit it, with the mate- 

 rials now at hand. 



Pecopteris pteroides, Brgt. Hist, des Veg. Foss., 1, p. 329, tab. 

 99, fig. 1. Specimen in the State Cabinet, from Mazon creek. 

 It is the only one which I have seen from the Coal Measures 

 of America. Coal No. 3. 



Pecopteris Cistii, Brgt. Hist, des Veg. Foss., 1, p.' 330, tab. 

 106, fig. 1 and 2. This specimen, also from Mazon creek, has 

 the nervation and the form of the leaflets of Pecopteris abbre- 

 viata, Brgt., and could be referred to this species, but for the 

 very narrow rachis. It is probably the upper part of a frond 

 of Pecopteris Cistii. 



Pecopteris polymorplm, Brgt. Hist, des Veg. Foss., 1, p. 331 

 and 332, tab. 13. (Pecopteris Miltoni, Brgt., Loc. Git.) It 

 abounds in fine specimens on the Wabash river, below New 

 Harmony, Indiana, and also at Grayville, Illinois; Upper Coal 

 Measures. 



56 Oct. 9, 1800. 



