884 FLORAL ZONES OF THE POTTSVILLE FORMATION. 



St. John. New Bnuiswick. With the exception of a few fragments 

 supposed to have come from the roof of Lykens coai No. 4 at Brook- 

 side, the species is not known below the Sewanee zone in the United 

 States. Its geographic distril>ution in this zone is wide, the same 

 form l)eing coUected in the shales over the Sharon coal in northwestern 

 Pennsylvania, the Sewell coal in the Virginia region, the Sewanee 

 coal in Tennessee, and in the coal-bearing shale in Washington County, 

 Arkansas. In the upper part of the Sewanee zone this plant appears to 

 merge into the form connnonly known as Pecopteria ijluim isa Artis. In 

 fact, in the region of the Fayette formation the latter appears to have 

 succeeded the New Hrutiswick fern. 



Alethopteris Lacoei sp. nov. 

 PI. CXCIII, Figs. 1. ± 



Secondary pinnfe linear-lanceolate, very long, acute, slighth' nar- 

 rowed at the base, often gently curved, with a distinctly lineate rachis; 

 ultimate pinna^ of moderate size, usually alternate, but often sub- 

 alternate, sub-opposite, or rarely opposite, open at nearly a right angle 

 to the rachis. usually close, sometimes slightly overlapping, more 

 rarelv a little distant, somewhat curved, linear-lanceolate, or linear, 

 tapering to a slender, acute point; rachis finely lineate, rather deeply 

 depressed, strongly concave and canaliculate ventrally. dorsally terete. 



Pinnules alternate or sub-alternate, the lowest open nearly to a 

 right angle, close or a little distant, slender, linear- triangular, or ovate- 

 triangular when small, hardly constricted at the base, tapering 

 o-entlv through the lower third, the margins converging a little 

 more rapidly in the upper two-thirds, acute or slightly obtusely 

 pointed, cut to near the rachis with a rather broad, acute sinus, regu- 

 larly and strongly crenulate-inflated in all portions of the frond; 

 lamina rather thin, very strongly ventrally convex, alternately 

 strongly inflated and transversly depressed at regular intervals of 

 from 1 to 2 mm., according to the size of the pinnules, the margins 

 being often slightly infolded dorsally so as to give the pinnules a 

 tapering acuminate apex. 



Ner\'ation distinct, regular; midrib moderately strong, hardly decur- 

 rent, straight, deeply depressed, tapering gradually, but distinct to the 

 apex: nervils slender, relatively regular, rather close, hardly decur- 

 rent, sim})le or forking once close to the base, and passing nearly 

 straight and ])arallt'l to tlie liorder. 



Ahtltoptri'ix. Ldcoci is one of the smaller or more delicate species of 

 tile geiuis, its forni and general proportions being closely comparable 

 to .1. .IA///AV//,' or the smaller. iiaiTow-pinnuled phases of .1. Av/- 

 c/iltica. It is, however, ver}'^ well marked by the alternating strong 



' Brongniiirt, Hist. vt-g. foss., \\. l'T.h, |.l. Ixxxiii, fiK^i. '■'>. in, 1. 



