Conus (Ximeniconus) oniscus (Woodring, 1928)

Description.

Shell small, biconic. Shoulder very low, rounded. Siphonal notch very shallow, siphonal fasciole low. Outer lip barely retractive, anal notch very
shallow. Anal fasciole forming a flat or slightly concave channel, bearing rather prominent retractive growth lines bent forward at the anterior edge.
On the early whorls the shoulder forms a rounded ridge due to a spiral thread.

Sculpture consisting of rather widely spaced low spiral threads on posterior half of body whorl, and of narrow spiral grooves bordered by similar threads on anterior half ⁽³⁾.

Length 37,3 mm.; diameter 15,8 mm. (holotype).

This small biconic species is represented by four specimens in the Henderson collection. The low shoulder and very shallow anal notch are unmistakable features. Some specimens from the Pliocene Waccamaw marl of South Carolina referred to C. marylandicus Green are
somewhat similar, but their shoulder, even on the later whorls, is a sharp-edged ridge and their anal notch is a little deeper.
Type material. Holotype (U. S. Nat. Mus. No. 369354) ⁽³⁾.

Diagnosis ⁽¹⁾.

Protoconch multispiral; early postnuclear whorls smooth with carinate shoulders; teleoconch sutural ramps with midsutural spiral fold; axial growth lines prominent on sutural ramps; subsutural flexure shallow and V-shaped; incised spiral grooves on anterior half, sometimes extending to shoulder.

Description ⁽¹⁾.

Shell dextral, moderately small to mediumsized. Last whorl conical to broadly and/or ventricosely conical; outline slightly convex to sigmoidal to nearly flat. Shoulder carinate to sharply angulate. Spire moderate to high; outline flat to slightly concave. Protoconch multispiral. Shoulders of early postnuclear whorls carinate. Teleoconch sutural ramps slightly concave to sigmoidal due to presence of midsutural spiral fold; axial growth lines usually prominent, outlining very shallow, angular (V-shaped) subsutural flexure. Last whorl with incised spiral grooves (forming ribs) on anterior half, sometimes extending to shoulder. Color pattern on last whorl consisting of ca. 20 rows of spiral dots along with two faint, discontinuous spiral bands that form axial streaks; teleoconch whorls with radial streaks.

Occurrence ⁽¹⁾.

The holotype of Conus oniscus (USNM 369354; Pl. 16, Figs 1-3) is from the Bowden Formation of Bowden, Jamaica.

This species is also known from the Caloosahatchee, Jackson Bluff , Tamiami (Pinecrest Beds), and Waccamaw formations of the southeastern U. S. One lot (UF 58070) is also known from the Bermont Formation.

Il Conus oniscus è molto simile al Conus marylandicus per forma e colorazione, ma ne differisce per alcuni sottocaratteri. La curvatura subsuturale è piatta o leggermente curvata nel Conus marylandicus mentre è decisamente angolata nel Conus oniscus. La rampa suturale del Conus marylandicus è piatta o leggermente concava, mentre nel Conus oniscus è sigmoidale ⁽¹⁾.

3D MODEL PRI 70612

Altezza massima 42 mm ⁽¹⁾