Report of the exploring expedition to the Rocky Mountains in the year 1842, and to Oregon and north California in the years 1843-44 . The aspect of the three last-named plants is more like that of the truecoal-measure ferns than any of the others; but the whole association, andtheir fossil condition, demand that they should be referred to a very modernperiod. New genus—trichopteris. Character.—Frond slender, flexuous, in tufts or single, branching orpinnate; branches long, very slender. 9. Trichopteris filamentosa. PI. 2, fig. 6. (No. 78 of collection.)Compare Fucoides asqualis, Brong. Hist. V
Report of the exploring expedition to the Rocky Mountains in the year 1842, and to Oregon and north California in the years 1843-44 . The aspect of the three last-named plants is more like that of the truecoal-measure ferns than any of the others; but the whole association, andtheir fossil condition, demand that they should be referred to a very modernperiod. New genus—trichopteris. Character.—Frond slender, flexuous, in tufts or single, branching orpinnate; branches long, very slender. 9. Trichopteris filamentosa. PI. 2, fig. 6. (No. 78 of collection.)Compare Fucoides asqualis, Brong. Hist. Veg. Foss., p. 58, t. 5, figs. 3 and 4. Description.—Frond pinnate or bipinnate; rachis long, and almost equal-ly slender throughout; branches numerous, regular, alternate, simple,•elongated, very slender, and flexuous. The branches are frequently folded back upon themselves, and undulated,lying like the finest thread upon the surface of the stone. This species iswety delicate and graceful, and can scarcely be examined without the aid of FOSSIL FERNS COLLECTION OF THE GEOGRAPHICAL SURVE)OT5EGON AND NORTH CALIFORNIA PL Jl. 307 [ 174 J a magnifier. This fossil is very similar to the Fucoides sequalis of Brong.,(from the lower chalk,) except that the branches are longer and undivided. 10. Trichopteris gracilis. PI. 1, fig. 5. (No. 84 of collection.)Description.—Slender, stems numerous, flexuaus, in a tuft, branched - branches numerous, slender, oblique, stronger than in the last species. This species is more robust than the first described, but evidently belongsto the same genus. I bad first supposed that this might be a collection offern stems, stripped of their foliage; but their slender structure, long;branches, and peculiar arrangement, with the appropriate proportion of altthe parts, forbid its reference to any thing of this kind ; it is therefore placedin a new genus. 11. Stems of ferns. PI. 1, fig. 7. The stems of ferns, denuded of leaves, and portions only of the
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