Identifier: annualreportofun2171geol (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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ordensis also occurs. Thishorizon corresponds closely with the Lunatia (Tylostoma) horizonabove the Requienia horizon of the Glen Rose section, as is shown byits near proximity to the Ostrea camelina zone, which occurs above it,206 feet from the top. JVerinea appears nearly a hundred feet abovethis bed, or 300 feet below the base of the Fredericksburg division,and ranges into it. One hundred and seventy-five feet below the baseof the Fredericksburg division there is a second horizon of MonopL ura,in a hard yellowish limestone, while 145 feet below is another zone ofJVerinea. In the upper 110 feet of the Colorado section, which homotaxiallymay represent the stratigraphic position of the lower Walnut andPaluxy beds of the northern sections, are numerous small fossils,including Exogyra texana(see PL XXVII), while Cardium mediale andLunatia (^Tylostoma) continue to the uppermost layers. Mr. Stanton lias recently determined the generic mime of this fossil to be Lunatia instead ofTylostoma.
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hill.-) PALEONTOLOGY OF THE GLEN ROSE FORMATION. 161 Ifrraminifera.—A peculiar fossil of the Glen Rose beds of theColorado section is the large foraminifer Orbitulina texana of Roemer,which occurs in a thick, chalky stratum adjacent to the-lower Lunatia(Tvlostoma) beds, about 220 feet below the summit of the beds in theColorado section. This fossil has not been noted north of the Coloradosection, but is a very marked and abundant species southward. Thechalky bed containing these shells was formerly exposed in the bed ofBull Creek west of Mount Barker, but has now been covered b)T thesediments from the Austin dam. Diller1 has noted the occurrence ofother species of Foramimfora in the matrix of the Orbitulina chalk,belonging to that genera. Echinoids are very rare, so far as known, in the Comanche Peaksection, and there are but few in the upper 100 feet of the Coloradosection, where a small species of Uolectypm abounds. The writer hascollected a few specimens of an irregular Epiaster-

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