Cyclonema varicosum

Classification
Phylum: Mollusca
Class: Gastropoda
Order: Euomphalina
Family: Platyceratidae
Genus: Cyclonema
Species: Cyclonema varicosum (Hall, 1861)

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1870 Cyclonema (ventricosa in error for ) varicosa Hall, Twenty-fourth Rep. N.Y. St. Mus. Nat. Hist., pl. VIII (Not defined).
1882 Cyclonema cincinnatiense Miller, Jour. Cin. Soc. Nat. Hist., vol. V, p. 230.

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Stratigraphic Occurrences

Geographic Occurrences

Map point data provided by iDigBio.

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Sequences (Formations)

C2 Sequence (Fairview?: Fairmount? Mount Hope?)
C1 Sequence (Lexington Limestone/Point Pleasant)

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Identification in Hand Sample

Three sizes of spiral riblike structure
Broadly conical spire and convex base
Impressed sutures
Lines are strong on all whorls, especially strong and oblique at aperture
Distinguished by its straight lip

Cyclonema varicosum from the Kope Formation of Foster, Kentucky (OUIP 33)

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Fossils of Ohio (1996):

Cyclonema varicosum Hall also has three sizes of spiral costae, but they are more prominent and the shell becomes larger than other species of the genus.

Thompson (1970):

Diagnosis. — Turbiniform shell with impressed sutures and wide ramp limited abaxially by a sharp cord, four to six prominent cords on body whorl separated by costae and threads, cancellated by strong lirae.
Description. — Coarse and heavy turbiniform shell, generally three poorly preserved whorls, nucleus unknown; sutures impressed, wide and sloping ramp limited abaxially by a sharp cord; whole profile convex, body whorl ventricose and expanded at aperture; aperture large and flattened on base; outer lip round and flaring; inner margin straight; columellar lip straight to lunate and excavated; coarse ornament of prominent sharp cords which approach carinae, four to six cords on body whorl decreasing to three on next two whorls, separated by a costa and many threads, cords becoming closer together toward periphery, all spiral ornament being: irregular and wrinkled; collabral lirae strong on all whorls, especially strong and oblique at aperture of large specimens; ornament present on each whorl preserved; seven to eight closely spaced cords on half of basal surface and upper surface of aperture.

Ulrich & Scofield (1897):

Though closely related to C. mediale this shell is still easily distinguished by its straighter columellar lip, fewer, stronger and sharper revolving and transverse surface markings, deeper suture and more convex whorls. The revolving ridges, especially those on the outer side of the whorls, are very strong and prominent. Between each two there usually several much thinner lines. Of the principal carinae the body whorl has only nine or ten, and of these only five or six are shown on the whorls above the last.

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