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Hall, James; 1811-1898 / Geological survey of Wisconsin, 1859-1863. Palaeontology. Part third
(1871)

II. Descriptions of fossils of the Niagara group,   pp. 7-90 PDF (23.8 MB)


Page 9


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     gradually attenuate. Principal aperture subeentral; arms originating
     close to the aperture, and curving in a spiral direction over the
     summit and along the sides to the point of greatest expansion, or
     sometimes a little below.
  The specimens of this species are from one to three inches in length,
with a diameter in the greatest expansion of from less than half an inch
to an inch and a half.
  The illustrations are of a large unsymmetrical specimen, and one of
symmetrical form somewhat smaller.
  Formation and Locality.-In the limestone at Racine, Wisconsin.
                     GOMPHOCYSTITES CLAVUS, N. S.
                           PLATE XIIa, FIG. 3.
Body clavate, gradually expanding to the upper part which is elongate
     ovate, nearly or quite symmetrical, summit regularly convex; prin-
     cipal aperture at the apex, and essentially central. Arms originating
     from one side of the central aperture, curving a little spirally down-
     wards, and reaching below the apex a distance about equal to the
     greatest diameter of the body.
  Below the expanded portion, the body becomes obtusely pentagonal, a
feature but obscurely shown in the cast; base unknown.
  This species is very nearly symmetrical, and much more gradually
expanding from below to the greatest diameter, and less abruptly rounded
above; while the arms have a more nearly vertical direction.
  It is possible that this may be only a modification in form of the G.
glans; but among a considerable number of specimens of that species, I
have not observed gradations to this form; and I therefore designate it
as a distinct species until it can be proved identical, or until its relations
with the preceding species can be more satisfactorily determined.
  Formation and Locality.-In the limestone at Racine, Wisconsin.
                  GENUS HOLOCYSTITES, N. G.
                        ['b27oc totus; Kvo7og, vesica ]
Body elongate, sub-cylindrical, elliptical or sub-ovate, composed of
    numerous (six or more) ranges of comparatively large plates, or
    of alternating series of large and small hexagonal or polygonal
      G. W.  2
                                  36


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