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abundant appearance Arundel Baltimore Band base beds Berry branches Bull character Cladophlebis clay closely common compared cones considerable County Cycadeoidea deposits described diameter distinct Dunker entire evidence feet ferns figured flora Fontaine formation forms Foss fossil Fredericksburg frond genus GEOLOGICAL Group Heer Hill identical included Jurassic known lateral leaf leaves length less lignite lobes localities Lower Cretaceous margin Maryland material National Museum nearly Neocomian nerves occur Onychiopsis Patapsco formation Patuxent pinnæ pinnules plants Plate Pleistocene Podozamites Portugal Potomac present preserved probably Professor rachis recorded referred remains represented resemblance sand Saporta Schenk Sequoia Seward side similar single slender slightly species specimens Sphenopteris suggest surface Surv Survey teeth thick U. S. Geol Upper usually various veins Virginia Ward Wealden width xlviii
Página 49 - Virginia ; a Geographical and Political Summary, embracing a description of the State, its geology, soils, minerals, and climate ; its animal and vegetable productions ; manufacturing and commercial facilities ; religious and educational advantages ; internal improvements and form of government.
Página 48 - Geological phenomena, and the deductions derivable therefrom, in 250 miles of sections, in parts of Virginia and Maryland. Also, notice of certain Fossil Acotyledonous Plants in the secondary strata of Fredericksburg...
Página 42 - ... of the formation to the Jurassic upon the evidence of the plants alone. " I do not, however, desire to be understood as arguing for the Jurassic age of the Potomac formation. The most that it is intended to claim is that, if the stratigraphical relations and the animal remains shall finally require its reference to the Jurassic, the plants do not present any serious obstacles to such reference.
Página 238 - Pteris, etc., to cast doubt upon the botanical affinity of Cladophlebis species unless these are attested by a considerable body of evidence. It is believed, however, that the Potomac species are all to be included in the subfamily...
Página 37 - ... to there is exposed another group of strata with which, at first view, the sandy and argillaceous layers of this formation might readily be confounded. These are the silicious, argillaceous, and pebbly beds, which, underlying the Tertiary in Virginia, and the well-marked Cretaceous formation farther north, have, in the latter region, been regarded as belonging to the base of the Cretaceous series of the Atlantic States. In Virginia the formation consists typically of a rather coarse and sometimes...
Página 176 - Dryosaurus has its nearest European ally in Hypsilophodon, again a Wealden type, and the crocodile, Goniopholis, is reported from the Wealden and its marine equivalent the Purbeckian, not from the older Jurassic levels. The weight of this evidence would seem to place this fauna beyond the Jurassic into the beginning of Cretaceous times.
Página 183 - It was not more than one-half the size of the western species, and its proportions were extremely slender. The bones are very light and hollow, the metapodials being much elongated and their walls extremely thin. An ungual phalanx of the manus measures about 25 mm. in length ; and 14 mm. in vertical diameter at the base. This animal could not have been more than 5 or 6 feet in length.
Página 38 - Fredericksburg containing similar remains, and to favor their being referred, at least in part, to the horizon of the upper Jurassic rocks. Possibly we may find here a passagegroup analogous to the Wealden of British geology.