86 FLORA OF LOWER COAL MEASURES OF MISSOURL 



(liniiiiishiiig- pinnatifid and simple pinnules; pinnules alternate, open, gen- 

 erally at or nearly at a right angle to the rachis, hardly decurrent except 

 near the apex or in the youngest pinnae, irregular, slightly unequal, seldom 

 parallel, sometimes slightly tipward curved, a little distant, close, or some- 

 times touching, oval or ovate, and cut to near the rachis by a slightly 

 decun-ent sinus when small, becoming oblong, or linear, the sides parallel, 

 usually uneven, the apex round, separated to the rachis or even slightly 

 constricted at the base by the decurrent sinus before becoming pinnatifid; 

 lowest pinnules of the pinna slightly reduoed, the uppermost pinnules par- 

 tially united with the ovate terminal pinnule; lamina dull, generally 

 opaque or minutely rugose, often rather broadly canaliculate over the mid- 

 rib, arching upward between the midrib and the margin, where it is often 

 flattened to form a narrow shallow gutter; nervation not very distinct; 

 midrib rather strong, sometimes slightly decurrent at the base, faintly 

 lineate, depressed to near the apex in the well-preserved fragments; lateral 

 nerves originating at a moderate angle, forking at a wide angle near the 

 midrib, the lower branch • curving to the margin, the upper branch arching 

 strongly near the midrib and forking again, the nervils passing out nearly 

 at a right angle to the border, the middle nervil forking again as the pin- 

 nule approaches the crenulate stage, those in the lobes of the pinnatifid 

 pinnules being rather close, curving strongly (Uitward, and forking again as 

 the lobes become more deeply dissected; fertile pinnte of the same form as 

 the sterile pinna?, a little more distant or slightly reduced; sori in a row, 

 situated within the border of the pinnule or lobe, often appearing as rathei* 

 large, noncontiguous, roundish, pustular elevations of the lamina on the 

 upper surface of the pinnule, or, when mature and crushed, seeming to 

 cover the lower surface ; sporangia oblong or lanceolate, obtuse or rounded 

 at the base, tapering above to an acute point, opening by a ventral cleft, 

 and attached apparently by or near the base in groups of four or more. 



When the first consignment of fossils from Henry Count}-, j\Iissouri, 

 was received at the United States National Museum, several years ago, I 

 attempted the identification of the species of Pecopteris, but foimd myself 

 entirely unable to distinguish, in practical usage, the thi-ee species described 

 and figured in the Coal Flora from this region. In fact, it immediately 

 became quite plain that not only were the same forms refeired to both 

 Pecopteris cUntoni Lx. and CaUipteridimn memhranaceum Lx., but it also 



