Conus amekiensis (Eames, 1957)

Conus amekiensis (Eames, 1957)

Description.

Of small-medium size, biconic. Protoconch rather tectiform, of three smooth, slightly convex whorls. Last whorl forming at least five-eighths of the height of the shell. Spire gently coeloconoid, of five to five and a half whorls with small nodes on an angulation close to the abapical suture; the narrow portion below the angulation vertical or sloping slightly inwards and causing a slightly imbricate appearance; upper part flattened or vaguely concave, shelving, with four or five spiral threads on its abapical two-thirds, the threads being slightly crenulated where crossed by the deeply concave growth-lines. Last whorl inverted-conic, shoulder with small, low nodes, base slightly excavated and neck slightly swollen; coarse, irregular spiral ribbons, which have narrow intervals and are fainter adapically, are vaguely beaded where crossed by low, flat ribs extending from the small nodes on the shoulder; the ribs are of about the same width as their intervals. Aperture narrow and parallel-sided, vaguely constricted near the abapical end, emarginate but not notched terminally.

REMARKS.

Conus parisiensis, with which Newton compared this species, is more produced abapically and has compound crenulations on the uppermost thread of the spire whorls (not small nodes on the lower angulation); its spiral ornament is not beaded and is restricted to the abapical half of the last whorl.

MATERIAL.

Several specimens, including the holotype (G.41837, Newton's fig. 9).

Conus (Leptoconus) amekiensis ⁽¹⁾

(Eames, 1957)

(Pl. 7, figs. 7 a-c)

Ameki Formation – Middle to Upper Eocene

Nigeria

Conospirus cf. parisiensis (Deshayes)

Newton 1922: p. 24, pl. 3, figs. 8-9.

Holotype G.41837: Newton's fig. 9

mm. 19 x 10

OCCURRENCE. Cuttings Nos. 1, 5, 6, 10, n, 12, 14, 15.

COLLECTOR. Mr. Kitson.

REMARKS. The small Coniform shells here determined as related to C. parisiensis of Deshayes from the Middle and Upper Eocene beds of Europe, are of fairly frequent occurrence in the Nigerian deposits. They are of more or less uniform dimensions, the largest measuring 19 by 10 mm., while those represented by figs. 8 and 9 of Plate 3 are a little under that size, the measurements of the type as given by Deshayes being 38 by 17 mm. The spire of widely conical and pagoda-like shape is composed of three smooth, elevated, embryonic whorls with an obtuse nucleus, while the succeeding whorls have a depresso-concave surface, furnished with a microscopically fine reticulate sculpture caused by the delicate spiral striations being crossed by longitudinal lineations which are deeply sinuated. Minute equidistant tubercles ornament the sutural margins, while the sculpture of the body-whorl is somewhat coarsely reticulate, the spiral costae being well pronounced and bearing regular tubercles at the junctions with the longitudinal striations. It is in some of these details that the Nigerian shells agree with C. parisiensis, although the latter has a less pagodiform spire and an ornamentation on the body-whorl which is much less accentuated, a difference, however, which may be due to erosion.


*Conus* *parisiensis* mm. 22,0 x 10,3 Eocene – Luteziano Chateau Rouge [AZFC N. 214-00]	Conus (Leptoconus) amekiensis (Eames, 1957) (Pl. 7, figs. 7 a-c) mm. 19 x 10

Bibliografia Consultata