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Conus arcuatus (Broderip & Soiwerby, 1829)
Conus arcuatus (Broderip & Soiwerby, 1829)[Gray, 1839]
Conus arcuatus vacuanus (Olsson, 1942)
Conus arcuatus (Broderip & Soiwerby, 1829)
This Cone, of which we have seen but one other specimen, is remarkable for its curved striæ and lip, which last is deeply notched at the termination next to the spire, so as almost to resemble the ala of some of the strombi. There are a few not very deep striæ at the base of the shell. Found in the Pacific Ocean, near Mazatlan.
Conus arcuatus vacuanus (Olsson, 1942)
Shell of medium size with a sharply angled shoulder and broadly conic, high spire; the nucleus was very small but is lost on all our specimens, it was followed by 10 or more spire whorls, the earliest of which are ornamented by small ribs which are quickly lost on the succeeding turns; the surface of the spire whorls is concave or excavated, leaving the edge of the shoulder sharply angular; the last whorl is rather wide at the shoulder, tapering rapidly forward into the anterior canal which is slightly twisted at the end; the sculpture, in the young stages, consists of strong, spiral grooves which cover the whole surface except the spire and possibly a narrow band adjacent to the shoulder ; these spiral bands are separated by strong grooves and generally average about 22 in number; these bands may be regular in size and width or they may be divided by medial lines; in older shells, a wide zone bordering the shoulder may be smooth or it may have only faint indications of the spiral bands remaining visible; columella straight, the anterior canal with a slight twist or fold at its end.
Length, 46 mm.; height, 22 mm. (type).
Length, 36 mm.; height, 18 mm.
This
cone recalls some Miocene species as C. planiliratus Sby. and
C. imitator liws Woodring. Like other members of this
group, the cone shows much variation in sculpture according to age
and size. Amongst Recent forms, the present shell is closely allied
to Conus arcuatus Sowerby. Conus gradatus, as figured
by Reeve, is possibly the same as Sowerby’s species. In the series
before me, the fossil differs by its wider form and shorter, more
evenly conic spire, the tip of which is scarcely attenuated.
A
cone from the Pleistocene of the Rio Guanabanon identified as C.
arcuatus is figured for comparison. ‘This shell is immature but
is very similar to the form figured by Reeve as C. gradatus.
(Plate 6 fig. 13)
Type.—Paleontological Research Institution,
No. 4030.
Occurrence.—Quebrada Pefiitas, Quebrada Mellisa and
Rio Guanabanon. .
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Bibliografia Consultata
