Conus cruzianus (Dall, 1890)

 

 

Shell elongate pyriform, thin, deeply spirally sulcated; whorls ten or twelve, apex acute, arising from a .spire but little elevated, and having its slope concave in profile; sides of the shell with about twenty deep, uniform rounded sulcations, separated by slightly narrower cords ; anteriorly these cords are  rounded and finely striated spirally, midway they are a little flattened, and  near the spine they are even marked with a shallow median sulcus; the channels are not striate between the cords, or but in the faintest manner; sides of the shell slightly swelling, falling away toward the spire, which is rounded at the margin, striated with fine distinct threads, and with a narrow striated channel close to and in front of the suture; transversely the sculpture is only of lines of growth, which cover the whole shell, but are not prominent ; aperture narrow, especially behind, posterior angle hardly notched, pillar straight, simple. Max. lon. of shell 27.5 ; of aperture 23.0 ; max. lat. of shell 13.3 mm. (2)



White Tertiary (Pliocene ?) limestones of the Island of Santa Cruz, West Indies
 (2). 


This shell, now pure white, retains traces of yellow flammules on the spire, radiating from the apex, and irregular yellowish blotches on the sides
 (2). 

This species is of entirely different form from C. planiliratus Sowerby, C. gracilissimus Guppy, C. aratus Gabb and other Antillean sulcate cones (2).

 

C. bonacsyi Gabb has also a widely different form, with the spire unstriated. I judge of Gabb's species, of course, by his types at Philadelphia, as the fossils have never been figured. I have had this species for a long time, and take this opportunity of figuring it (2). 

 

 

St. Croix is the only one of the islands between Vieques and the Anegada Passage that is known to have any Miocene beds, which again consist of limestone carrying Orthaulax aguadillensis Maury. It seems quite safe to correlate this Orthaulax-bearing limestone with the Quebradillas limestone, which is widespread and transgressive in Porto Rico and along the south edge of the Virgin Bank. St. Croix is the type locality of Conus cruzianus Dall, which seems to have been ignored. It probably was collected from the lower Miocene limestone (3).

 

 


Conus sextoni (Hoerle, 1976)

 

 

Diagnosis (1):

 

Shell low spired; slender; periphery about one-fourth distance in front of shoulder; tapering anteriorly with a suggestion of a slight twist to the left. Adult specimen consisting of two and one-half rounded nuclear whorls and seven teleoconch whorls. Sutures distinct, slightly impressed. Summits of early post-nuclear whorls flat, those of later whorls convex with an adaxial slope, forming a slight concavity in front of suture.

Whorls ornamented by prominent, but not crowded, moderately arched growth lines. Anal notch shallow; outer lip nearly straight. Sculpture of last whorl consisting of broad , flat bands separated by narrow, increm entally striated grooves; growth lines prominent, giving the shell an axially roughened appearance.

 

Dimensions of holotype: height 19.0 mm (incomplete), diameter 9.2 mm.

Holotype: USNM 647645.

Type locality: TU 951, Ten Mile Creek, about 1 ¼  miles west of Chipola River (SE ¼  Sec. 12, T1N, R10W), Calhoun County, Florida.

Occurrence: Chipola Formation, Florida; late lower Miocene.

 

Figured specimen: USNM 647645. (holotype).

 

Discussion: C. sextoni is represented only by the type specimen and does not appear to be allied to any other Conus species from the Chipola Formation. It cannot definitely be stated at this time if the bands and narrow grooves, completely covering the final whorl, are a constant feature of this species as, generally, the extent of ornamentation of the last whorl is a variable factor, e.g., C. chipolanus Dall. The two and onehalf whorl nucleus, the lack of ornamentation of the early whorls and the uniquely formed summits of the spire whorls easily differentiate this species from ot her Conus of the Alum Bluff Group. The only other fossil cone to which this new species bears a resemblance, and only superficially, is C. cruzianus Dall, 1890, from the Pliocene limestone of the " Island of Santa Cruz, West Indies" [St. Croix, U.S. Virgin Islands]. The one feature C. sextoni and C. cruzianus have in common is a slight channel in front of the suture. The ornamentation on the last whorl of C. cruzianus consists of rounded, finely striated cords, the posterior ones medially sulcated , as contrasted to the bands and grooves of C. sextoni.

 

A Recent Caribbean species, C. granulatus Linne , 1758, has the final whorl sculpture similar to C. sextoni but the spire characteristics are entirely different. Treatment failed to reveal any color pattern and so it must be assumed that in life the shell was unpatterned, unlike C. granulatus, which has strong shoulder mar kings.

This shell is named in honor of Mr. Cecil Sexton, Altha, Florida, who has generously permitted workers to collect at TU 951, which is located on his property.

 

 

 

 

 


 

 

 

Conus sextoni (1)

Holotype, USNM 647645

mm. 19,0 x 9,2

Chipola Formation, Florida

Miocene

Conus cruzianus (2)

mm. 27,5 x 13,3

Pliocene ?

Island of Santa Cruz, West Indies

 

 

 

 

 

 


Bibliografia Consultata

 

·         (1) - Hoerle, S. E., 1976. The Genus Conus (Mollusca: Gastropoda) from the Alum Bluff Group of Northwestern Florida. Tulane Studies in Geology and Paleontology, 12 (1 )

·         (2) - Dall, W. H., 1890. Tertiary Mollusks of Florida. Transactions of the Wagner Free Institute of Science of Philadelphia, 3

·         (3) - Woodring (1928) “MIOCENE MOLLUSKS FROM BOWDEN, JAMAICA PART II GASTROPODS AND DISCUSSION OF RESULTS