Cyclonema bilix lata

Phylum: Mollusca
Class: Gastropoda
Order: Euomphalina
Family: Platyceratidae
Genus: Cyclonema
Species: Cyclonema bilix lata Meek, 1873

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Stratigraphic Occurrences

Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C4 (Arnheim)
  • C5 (Waynesville)

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Identification in Hand Sample

  • Medial groove in largest whorl
  • Trochiform shell
  • Sutures incised
  • Aperture polygonal to square
  • 11 to 12 chords on body whorl

Cyclonema bilix lata from the Waynesville Formation of Cincinnati, Ohio (OUIP 1699)

Cyclonema bilix lata  (Click to view in 3D!)
Cyclonema bilix lata (Click to view in 3D!)
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Davis (1998):

  • Gastropod. Characterized by a medial groove in the largest whorl.

Thompson (1970):

  • Diagnosis. — Cyclonema bilix with concave whorl profile, undulating surface of growth ridges, medial depression, and flaring base on body whorl.
  • Description — Distinctly trochiform shell, whorl profile concave, medial groove in lower two whorls, lower half of body whorl flaring outward below depression, rounded periphery at base of whorls. Sutures generally incised, may be channeled; upper shoulder narrow, rounded to angular; basal surface flattened. Aperture generally polygonal to square, rarely round; inner lip channeled, thin and straight in small specimens, thickened and lunate in large oiks; outer lip thin and commonly reflexed. Ornament delicate and variable, three orders of ornament: cords, costae, and one thread on body whorl, or of two orders: cords and one to three threads on body whorl, or one order of undifferentiated spiral lines, 11 to 12 cords on body whorl, penultimate whorl has cords and costae, antipenultimate whorl has cords only; collabral lirae delicate to coarse and may cause pitted pattern, strong growth wrinkles abundant on body whorl produce undulated surface.

Miller (1874):

  • Shell turbinate, depressed; breadth greater than the length; volutions four or five increasing rapidly in size, the first one flattened on the under side; aperture suboval, oblique; suture broad and deep; inner lip thickened, outer lip thin and sharp. Surface marked by revolving lines, varying in size and distinctness, in some examples being sharp and prominent, in others scarcely visible to the naked eye, crossed by fine striae, or lines of growth, which, to the sharply defined ones, give the shell a beautifully ornamented appearance. Volutions with oblique undulations, and a broad revolving depression near or above the center, most conspicuous on the body whorls, sometimes extending to the apex.
  • Height of a large specimen about 1.25 inches, breadth 1.5 inches. Small ones, less than 5/8ths of an inch in height and breadth.
  • The above is the typical form, but examples are found varying gradually to a narrow body whorl, narrow, shallow suture, and conical form, and decidedly longer than wide; all having the peculiar wavy or undulating surface more or less distinct, with other features in common, so that it is impossible, or very difficult, to find a dividing line.

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