STRATIGRAPHY OF THE SKYKOMISH BASIN 



571 



Fort Union beds. Three ferns are represented by abundant speci- 

 mens of Asplenium and Pteris in the shales of F 831 and F 831+50. 



Genus Asplenium 

 Asplenium magnum var. intermedium var. novum (Duror) (Fig. 3) 

 Knowlton: "Fossil Flora of Yellowstone Park," extract, Mono. XXXIII, 



U.S.G.S., 1899, Part 2, p. 667; PL LXXIX, Figs. 8, 8a. 

 Heer: Flora Foss. Arct., Vol. IV, "Ostsibriens," Taf. XX (A. whitbiense). 



This form is so named because it is intermediate in character 

 between A. magnum (Knowlton) and A. whitbiense (Heer). The 

 frond is not pinnate, but the lobes are cleft one-half to one-third 

 of the distance to the rachis. The margin of the lobes is entire. 

 These lobes are one and one-half to twice as long (along midvein) 

 as broad and come to a rounded point. 

 Secondary veins come off at an angle of 

 about 45 , members of each pair being 

 almost opposite. Each secondary bears 

 eight to ten pairs of tertiaries, which are 

 generally once forked. A few rare cases of 

 simple secondaries and still fewer twice- 

 forked secondaries were observed. The 

 variety differs from A . magnum of Knowlton 

 in possessing almost deltoid instead of ovate 

 lobes and in being rather larger. This form 

 is separated from A . whitbiense of Heer, because here most second- 

 aries fork once only, and because Heer's form has true pinnules— 

 the form being bipinnate. There is no sug- 

 gestion that this form is fully even once 



pinnate. 



Genus Pteris 



Pteris pennaeformis (Heer) (Fig. 4) 

 O. Heer: Fl. Tert. Helvetiae (1855), p. 38; Taf. XII, 

 Fig. la-d; Miocene age. 

 Lesquereux: Tert. Flora (1878), p. 52; PL IV, Figs. 3, 4, Pseudopennae- 

 formis, Lower Lignitic age. 



The Cascade specimens are quite similar to that figured by 

 Heer, except that here only that part of the pinnae with entire 



Fig. 3 . — A splenium 

 magnum var. inter- 

 medium var. novum. 

 (| natural size.) 



Fig. 4. — Pteris pennae- 

 formis. Q natural size.) 



