Maryland Geological Survey 353 



Considerable variability is shown among the various forms but not 

 enough to warrant specific distinctions. The specimen named C tenopteris 

 minor by Fontaine is simply a small form of the type as the latter 

 author suspected. The marginal toothing is quite a variable feature on 

 a single specimen of any size, and the form named Ctenopteris virginien- 

 sis by Fontaine shows a variation in the venation in the direction of the 

 genus Scleropteris, the veins being apparently aggregated into two 

 bundles at their insertion on the rachis, although this feature is far from 

 clear on the specimens, the coriaceous nature of the pinnules rendering 

 the venation indistinct and quite unlike the diagrammatical figures of 

 these forms which were originally published. 



Occurrence. — Patuxent FoRMATioisr. Fredericksburg, and near Po- 

 tomac Eun, Virginia. Arundel Formation. Langdon, District of 

 Columbia. 



Collection. — U. S. ISTational Museum. 



Ctenopteris angustifolia Fontaine 



Ctenopteris nngustifoUa Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 159, pi. Ixv, fig. 2; pi. Ixvii, fig. 4. 

 Ctenopteris angustifolia Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv., 



vol. xlvlii, 1905, p. 510. 



Description. — "Frond unknown; ultimate pinnge long, with rather 

 stout rachises, pinnules linear or liarrowly oblong, in proportion to 

 width quite long, slightly curved forM^ards, separate to the base, or united 

 to form a vdng on the rachis of the pinnae, cut away obliquely on the 

 up]3er side at base, and slightly decurrent on the lower side, attached 

 by the entire base, terminated by from one to three acute spinous teeth, 

 and ha^dng a varying number of the same placed irregularly on both 

 margins. The nerves proceed from the rachis at different points along 

 the entire base of the pinnules; the outer ones simple or forking once, 

 the central ones forking several times, the ultimate branches being long, 

 slender, and slightly diverging." — Fontaine. 1890. 



