636 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.38. 



Kootenai of Montana, the latter forms at least, being probably 

 identical with the Virginia species. 



Occurrence. — Patuxent formation. Fredericksburg, near Tele- 

 graph station and near Potomac Run, Virginia. 



Collections. — IT. S. National Museum. 



THE GENUS NILSONIA OF BRONGNIART. 



This genus was founded by Brongniart ° for certain remains from 

 the Rhaetic of Sweden which had been recorded and figured by 

 Nilsson in 1820 who regarded them as fern remains. In the Prod- 

 rome the diagnosis is as follows: 



Feuilles pinnees; pinnules rapprochees, oblongues, plus ou moins alonge'es, 

 arrondies au sommet, adherentes au rachis par toute la largeur de Ieur base, a nervures 

 paralleles, dont quelques-unes sont beaucoup plus marquees. & 



The genus was regarded by Brongniart as referable to the Cycadales 

 a view generally accepted by subsequent workers, although Schenk" 

 in 1867, on the basis of supposed sori on some German specimens, 

 referred it to the Filicales, in which he was at first followed by 

 Schimper d and more recently by Solms-Laubach. 6 



The genus has also been ably discussed by Saporta, Nathorst, 

 Seward, and others, Nathorst in particular having shown that the 

 two kinds of veins supposed to occur together w T ere due to slight folds 

 in the lamina due to pressure, maceration, or the creep of the enclosing 

 strata. He characterizes the veins as equal and simple and empha- 

 sizes the insertion of the lamina on the upper surface of the rachis, 

 suggesting that Schenk's supposed sori are fungal or stomatal in 

 their nature/ 



The genus may be redefined in the following terms: Frond coria- 

 ceous, elongate-lanceolate in outline, entire or commonly more or 

 less deeply pinnatifid by being split, usually to the rachis, into a 

 number of more or less irregular segments which are contiguous, 

 usually broad, and truncate. Lamina attached to the upper surface 

 of the rachis, the simple and parallel equal lateral veins running 

 almost or quite to the median line. In material showing only the 

 under surface of the fronds the stout midrib is prominent and un- 

 segmented specimens are scarcely distinguishable from Tsrnwptcris 

 and allied forms, while the segmented varieties approach Anomoza- 

 mites or even some species of PterophyUum in appearance. 



" Ann. Sci. Nat., vol. 4, 1825, p. 218. 

 & Brongniart, Prodrome, 1828, p. 95. 



c Schenk, Die fossile Flora Grenzschichten Reapers u. Lias Frankens, L867, p. 124. 

 <i Schimper, Pal. Vegel;., vol. 1, 1869, p. 488. 

 f Solins-Laubach, Fossil, Botany, L891, p. L39. 



/Sec Nathorst, fiber die gattung Nilssonia Brongn., Kongl. Svenska Vet. akad. 

 llaii.ll., vol. 4:5, L909, No. 12. 



