Leptoconus
cuspidatus (Tate, 1890)
Description.
Shell conoidal, about twice as long as wide, width a flat or very low spire ; spirally fine-ribbed on the spire and at the base, otherwise usually smooth. Spire consisting of seven whorls separated by a well-defined, impressed, linear suture with rudely crenate margins ; ornamented spirally by flatly-rounded unequally-sized threads (usually about nine en the penultimate whorl), varying somewhat in thickness, but usually as wide as the interstitial furrows, crossed by incurved growth-lines (1).
The spire terminates in a slender, pyramidal, acutely-pointed pullus
consisting of five smooth moderately convex whorls of slow increase. Body-whorl obtusely angled at the
periphery, regularly tapering to
about three-fourths of its height where it is slightly constricted; ornamented
with sigmoid striae of growth, and in the anterior-fourth by wrinkled threads,
narrower than the interspaces. Some young
shells have punctated impressed lines on the body-whorl (1).
Dimensions. — Total length, 58 mm.; greatest diameter, 30
mm.; length of aperture, 56 mm.; length and breadth of pullus, 2 mm.
Localities. — Rather common in the lower beds at Muddy Creek, and in the blue clays at Schnapper
Point. Calciferous sandstones of
the River Murray Cliffs near Morgan.
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Conus cuspidatus (1) Vol
XIII – Pl. VII – Fig. 1 Eocene
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Conus cuspidatus Fossil Beach
Victoria Australia Middle Miocene [Coll. Angus
Hawke] |
Protoconch small, composed of two and a half smooth turns, indistinctly striated with growth-lines anteriorly; posterior portion slightly oblique with reference to the axis of the shell. Spire elevated, acute, convex, about one-sixth the total length of the shell; spire-whorls seven in number, staged, excavated, spiral lineations bold and continuous, growth-lines prominent, sinuated. Keel sharp and plain, not being crenulated even in the brephic stage. Body-whorl elongate, ornamented throughout its length by distant spiral sulcations which are punctated where crossed by the lines of growth. Aperture long and narrow; outer margin thin and arched ; posterior sinus very deep ; anteriorly the aperture is somewhat dilated and the columella is slightly twisted (3).
The elongation and narrowness of the body-whorl are distinctive features. Its nearest ally in the Australian Tertiaries is C. extenuatus (Tate, 1890) which, however, is broader, whilst its body-whorl is not so long, its periphery is not so sharply keeled, the earlier whorls are crenulated, and the ornamentation of the spire differs. C. newtoni closely resembles C. sieboldi (Reeve) (3).
Characteristic
gastropod of the Mediterranean-Iranian Province is, among many others, Conus
(Leptoconus) diversiformis (2).
Widespread
species which are recorded from both provinces and are therefore diagnostic
(typical) of the entire Western Tethys Region are Conus diversiformis
Deshayes, Conus carcarensis Sacco (2).
Bibliografia Consultata
·
(1)
- Transaction of the Royal Society of South Australia - v.13 (1889-1890) - pag.
199
·
(2)
- Auckland Museum’s natural sciences, human history and documentary heritage
collections
·
(3) - Catalogue of the tertiary mollusca in the Department of Geology.
Part I. Australasia