Cyclonema simulans

Phylum: Mollusca
Class: Gastropoda
Order: Euomphalina
Family: Platyceratidae
Genus: Cyclonema
Species: Cyclonema simulans Ulrich, 1897

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  • 1897 Cyclonema simulans Ulrich, Geol. Minnesota, 3, pt. 2, p. 1061, pl. 78, fig. 47.
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    Stratigraphic Occurrences

    Geographic Occurrences

    Map point data provided by iDigBio.
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    Sequences (Formations)

    • C2 Sequence (Mt. Hope)
    • C3 Sequence (Corryville)

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    Identification in Hand Sample

    • Shell flattened, up to three whorls preserved
    • Surface marking consist of revolving and obliquely transverse lines
    • Broadly conical spire and convex base
    • Turbiniform, broadly convex in whorl profile

    Cyclonema simulans from Mt. Hope formation of Hamilton County, Ohio (CMCIP 19905)

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    Thompson (1970):

    • Diagnosis. — Turbiniform and broadly convex in whorl profile, apertural margin strongly oblique and arched onto body whorl forming a horizontal shoulder, spiral cords obscured at aperture by growth wrinkles.
    • Description. — Turbiniform, shell flattened, up to three whorls preserved, partial apex indicates a rapidly planispiral termination at fourth whorl; whorl profile usually convex but may be straight, periphery varies from center of convex whorls to base of flattened whorls; sutures variable: impressed to incised to channeled, shoulder rounded to angular; outer lip round and strongly oblique abapcrmrally, arching onto body whorl and forming a horizontal shoulder at apertural margin; inner margin may be straight, irregular, or concave; columellar lip thickened and excavated; ornament of one order of spiral cords, equal-sized and distant, 10-15 on body whorl, crossed by distinct growth lirae parallel to oblique aperture, forming growth wrinkles at aperture which obscure spiral ornament, ornament extending through antipenultimate whorl, basal surface ornamented only by lirae.

    Ulrich & Scofield (1897):

    • Of this species we have about fifty specimens. These show that the shell is of medium size, with a general form about intermediate between C. humerosum and C. mediale, though rather nearer the former, there being usually a small shoulder and a flattening or even a slight concavity of the outer slope of the last whorl. It is distinguished from both by its surface markings. These consist as usual of revolving and obliquely transverse lines, but the former are much weaker on the last two whorls and often quite obsolete near the mouth, while the latter are more distant excepting in the last third of the body whorl of old examples. In the latter the mouth is sometimes irregularly expanded and thrown upward along the suture.
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