114 FLOKA OF LOWER COAL MEASUKFS OF MISSOURI. 



alternate or subopposite, open, linear-lanceolate, somewhat contracted at the 

 base, close or sHghtly overlapping, provided with tertiary pinnse below, pin- 

 natifid near the apex; ultimate pinnae subopposite, subalternate or alternate, 

 close, rarely touching, very open, linear-lanceolate, very long, usually 

 slightly narrowed at the base, the sides nearly parallel in the middle 

 portion, tapering gradually to an acute apex, 1.5 to 20 cm. or more in 

 length, .5 to 3 cm. in width, becoming connate at the base by a narrow 

 decurrent lamina and succeeded by diminishing pinnatifid pinnules in pass- 

 ing upward; pinnules subopposite, subalternate or alternate, very open, 

 seldom touching, irregular in angle and length on the same pinna, 3 to 

 18 mm. long, 2 to 4 mm. wide, but very little if at all contracted near 

 the base, the sides nearly parallel, obtusely rounded or round at the apex, 

 the upper surface strongly convex and bordered often by a marginal shal- 

 low canal or gutter; lamina thick, dull, and always uniting the pinnules at 

 the base, the sinus being rounded, and slightly decurrent only between the 

 largest pinnules; midrib strong, hardly decurrent, deeply depressed on the 

 upper side, broad and striate beneath, and terminating abruptly at a dis- 

 tance from the apex nearly equal to the average width of the lateral lamina ; 

 nerves few, very distant, often obscure on the upper surface, more distinct 

 beneath, originating from botla rachis and midrib, nearly straight or arching 

 slightly in the larger pinnules, oblique in the smaller pinnules, simple or 

 sometimes forking at or near the base, rarely forking above the middle, and 

 passing nearly at a right angle to the iiiargin, where they number about 

 30 to the ceiitimeter. 



A typical example of the mature portions of this well-marked and 

 characteristic species in the fossil flora of Missouri is illustrated by Professor 

 Lesquereux in fig. 1, pi. xxxi, of the Coal Flora. As there shown, the 

 irregular character of the open, parallel-sided connate pinnules, with the 

 verv distant nerves springing from the disproportionatel}' thick midribs, is 

 well brouglit out. 



As remarked in the original description, the nerves of the thick pinnules 

 sometimes appear more numerous than they really are. Frequently the 

 flattened border is not distinct, though it often is so developed as to form 

 a shallow gutter or canal about the margin of the pinnule, as seen from 

 above, or a marginal band as it appears from below. The midrib, which is 

 hardly deciirrent, is strongly depressed above, broad, and conspicuously 



