88 FLORA OF LOWER COAL MEASURES OF MISSOURL 



The segments on the large slaljs are also of importance as showing in 

 direct connection on the same pinna the acute or acuminate apices of the 

 lateral compound pinnse, some variation in the obtuseness of the ultimate 

 pinna% and, in particular, the presence of slightly macerated portions in 

 which the pinnules are flattened and spread out, in contrast to the well- 

 preserved portions, in which the lamina is arched and broadly canaliculate 

 over the midrilj, so as to give the pinna^ an Alethopteroid aspect. The 

 superficial characters seen in the upper lateral pinnaj in the center of the 

 large slab will at once be recognized in Fig. 1, PI. XXXI, one of the figured 

 types^ of Alethopteris amhigua Lx. (No. 3093, Lacoe collection), and the 

 detail of the nervation in the latter (PI. XXXI, Fig. Irt) agrees equally 

 well. The original (No. 3094, Lacoe collection) of fig. 3 of the same plate 

 in the Coal Flora presents precisely the same features, both in the form and 

 in the details, as is seen in the type of fig. 2, both specimens^ being unques- 

 tionable representatives of the species illustrated in PI. XXIX. 



The reference of Nos. 3093, 3094, 3095, 3096, and a number of other 

 Missom-i specimens of this form to Alethopteris was presumedly due to the 

 irregularity of the pinnules and the rather strongly depressed midrib, sug- 

 gestive of Aletliopteris amhigua, as well as to the scarcity of the smaller and 

 pinnatifid fragments of the latter species in the author's hands at the time 

 the description was written. The real difference of the nervation of the 

 two species, which will be illustrated in Pis. XXVIII, XXXIII, and 

 XXVI, Fig. Ifl, is indicated even in figs. Iff and 3ff of the plate in the 

 Coal Flora. 



The same conclusion as to specific identity is to be di-awn from the 

 details of No. 3174, Fig. 1, PI. XXVIII, which was one of the types used 

 in Professor Lesquereux's original description of P. dintoni. No. 3179 and 

 several other examples from Missouri in the same collection are also frag- 

 ments of the same plant, being quite easily distinguishable from the other 

 form originally included in the species last mentioned. 



The pinnte seen in PI. XXX are presumabl}' from the middle or lower 

 portions of the frond. Toward the extremity of the large pimije corre- 

 sponding to those on the large slab, the rachis tapers quite rapidly, the 



I Coal Flora, vol. i, p. 182, pi. xxxi, fig. 2. 



-Unfortunately tlie original of tig. 3 of pi. xxxi of the Coal Flora is not snited to illustration 

 \)j pliotograpliv. 



