Parvanachis obesa (C. B. Adams, 1845)

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Parvanachis obesa (C. B. Adams, 1845)

Abbott describes P. obesa as 4-7 mm, moderately wide, dull-grayish with 1-2 subdued, spiral brown bands in some specimens. Small, sharp axial ribs with spiral incised lines not crossing the ribs. There is a fairly strong, occasionally knobbed, subsutural spiral cord. Mature shells have a large, smooth and rounded varix on dorsum of the lip. Body whorl just behind varix has a smooth spot. Inside of lip with 3-5 small teeth. Radwin notes that the whorls of P. obesa are barely convex, the columella is also minutely dentriculate, shell surface is glossy with a thin brown periostracum, and color pattern is ivory with brown markings and sometimes having isolated spots on the apertural lip, some forms in which the entire shell is purplish-brown. Radwin contradicts Abbott when he indicates the axial ribs are crossed by strong spiral cords. In my experience, Abbott's characterization of "spiral incised lines not crossing the ribs" is more accurate. Radwin's "strong spiral cords" are more characteristic of P. ostreicola, which he describes as having a reticulate sculpture.

I have found living populations of P. obesa on both sides of Florida, but not in the Keys. As indidcated by Radwin, P. obesa appears to be found in sandy or sand and grass habitats and is not found in association with oysters.

The following series of images illustrate the characters described by Abbott and Radwin.

Palm Beach Inlet Lagoon, Palm Beach County. 5 mm


Sebastian Inlet Lagoon, Indian River County. 5.2 mm

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The below image portrays the "fairly strong, occasionally knobbed, subsutural spiral cord," " large, smooth and rounded varix on dorsum of the lip," smooth spot just behind the varix, and the "thin brown periostracum."

Blind Pass Inlet, Pinellas County. 4.5 mm


The following image is an attempt to highlight the dentriculation on both the inside of the outer lip and the columella.

Sebastian Inlet Lagoon, Indian River County.


Closeup of the protoconch of the specimen from Palm Beach Inlet Lagoon.

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reserved