140 FLORA OF LOWER COAL MEASURES OF MISSOURI. 



the distinction and validit-\- of the form to whieli I have consequentlA' given 

 the above specific name. 



Tlie name Didijopteris, for which Presl substitnted Linopteris, shoukl 

 no long'er be employed in the terminology of fossil ferns, since, as Potoni^ 

 points ont, the same name, which was earlier applied by Lamouronx (1809) 

 to a genus of living Algte, is still recognized in tlie family Dictyotacece 



The essential characters of Linopteris gilkersonensis are the nearly 

 straight and rather small pinnules, the sides converging slightly or nearly 

 ^Darallel, the apex rounded with almost bilateral symmetry; the coarseness 

 of the nerves, the general direction of which is very oblique to the margin; 

 the relatively small number of the areoles, which are proportionately very 

 broad and consequently few in number, the inner ang'les being- unusually 

 open. It differs from the group represented by L. obliqua Bunb., L. suh- 

 Brongniartii, or L. BrongmartU (Eichw.) by the straighter pinnules, the 

 coarse veins, and the relatively few and broad meshes. Although resem- 

 bling in form and size some of the specimens figured by Kidston^ and 

 Zeiller^ as Bictyopteris Munsteri Roem., the strong' nervatioi^ rigid and 

 open-ang-led nerves, with shorter meshes at the margin, make it improper 

 to associate the specimens in hand with that species. 



Locality.— GiWevsonh Ford, U. S. Nat. Mus., 548.5. 



T.ENIOPTERIS Brongiiiart, 1828. 

 Prodrome, p. 61; Hist. v(^g. loss., vol. i, 18,31 or 1832, p. 262. 



T.^NI0PTERIS ? MISSOUIilENSIS D. W. 



PL XL, Figs. 1-7. 

 1893. Twniopteris 7nissouriensis D. White, Bull. Geol. Soc. Am., vol. iv, p. 119, pi. i. 



Fronds bipinnate (tripinnate ?), the larger divisions linear-lanceolate, 

 acute, composed of pinnatifid pinnules near the base, above which are simple 

 pinnules; primary rachis broad, shining, marked by somewhat irregular 

 lines, and consisting of a thickened central portion, broadly but shallowly 

 canaliculate above, half round below, and of thinner marginal laminse; pin- 

 nules opposite, subopposite, or alternate, slightly distant, at right angles or 

 reflexed below, becoming more oblique above, ribbonlike, gradually taper- 



' Foss. Fl. Radstock Series, 1887, p. ,S61, pi. xxi, figs. Ha-b. 



'' Fl. foss. houill. Valenciennes, Atlas, 1886, pi. xliv, figs. 2, 2a ; see also figs. 1, 3, 4, 5. 



