Cerion microdon Pilsbry & Vanatta, 1896

Original Description

"Shell varying from cylindric to stout oval, strong and solid; whit­ish with some inconspicuous gray flecks. Whorls 8½ to 9½, the first one smooth, next finely and regularly costellate, following whorls with coarser riblets becoming regular, curved, moderately coarse ribs on the cylindrical portion, on base of last whorl obsolete or subobsolete. Latter 3 to 4 whorls of about equal diameter, those above forming rather a long cone. Aperture rounded, truncate above, white within. Peristome white, narrowly expanded and reflexed, obtuse; parietal callus very thin or moderate. Axial fold incon­spicuous from in front; parietal tooth extremely small, short.

Alt. 21½, diam. l0½; alt. of aperture 8½ mm.

Alt. 19½, diam. 9½; alt. of aperture 8 mm.

Alt. 18½, diam. 10; alt. of aperture 7 mm.


         While this species is very much smaller than C. incrassatum, and has the parietal tooth extremely small or almost obsolete, still in figure and sculpture it resembles the larger shell, and may be con­sidered a variety of it until further information is received.

         C. incrassatum, like the very closely allied C. dimidiatum, has a smooth form which intergrades with the stoutly ribbed typical shells. The earlier whorls have the minute sculpture as in the type form, but to the unaided eye the surface appears smooth."

(Pilsbry & Vanatta, 1896:328-329)

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