Conus dennanti

Lithoconus dennanti (Tate, 1892)

Description.

Conus dennanti

(Conus pullulascens var.)⁽¹⁾

Plate XI fig. 7

This species does not appear to be described, except in the explanation of the plate above cited, where the following words occur: " Conus dennanti, sp. nov. (C. pullulascens, var., Tate)."

The protoconch (Plate II. Figs. 8a-b) differs from that of C. pullulascens in not being angulate, or turbinate ; it is composed of three smooth, convex turns, imbedded in the crown of the shell, being in fact the only part which stands above the flat surface produced by the convolution of the shell-whorls proper. This upper surface is much depressed, has linear sutures, and is boldly, spirally striated. The periphery of the body-whorl is more sharply keeled than any other Australian Tertiary Conus; the surface of the whorl is covered by rather closely-set spiral lineations and sinuous growth-lines. Aperture very narrow, outer border parallel with the inner, but slightly dilated anteriorly; columella twisted in front ⁽²⁾.

Dimensions. - Length 33 mm. ; breadth 20 mm. ⁽²⁾

Form, and Loc. - Eocene: Victoria. ⁽²⁾

70423. One specimen ; from Meribee Plains. Purchased ⁽²⁾.

G. 5493. Two specimens ; from Muddy Creek. Purchased ⁽²⁾.

Conus dennanti ⁽²⁾

During the transgression of the Miocene sea upon the Australian continent, great thicknesses of sediments, as clays and shell-marls, with occasional greensands, were laid down, particularly along the coast-line of that period. Both on sea of sea-urchins and other animal forms, reached in many cases their maximum stage of development. Australia shared in this feast "I fat things, which was spread .it the time over many parts of the world, and her Miocene marine fauna consequently yields an occasional specimen of gigantic proportions compared with similar forms and species from the older and younger rooks of the Tertiary series ⁽³⁾.

One such greatly developed form. which seems worthy of notice, is the shell of a Conus found by Mr. W. J. Parr in the Bird Rock Cliffs, Torquay, and lately presented by him to the National Museum. It belongs to Tate's species, Conus dennanti, a form which shows certain affinities to C. pullulascens T. -Woods. It differs from that species in the flat or even concave spire, a character which remains pretty constant, as well as in the non-angulate or turbinate protoconch, as pointed out by G. F. Harris, who, by the way, furnishes a good description of this shell ⁽³⁾.

The length of the large specimen from the Bird Rock Cliffs is 88 mm., with a width, at the apical end, of 60 mm. The largest specimen of C. dennanti in the Dennant collection at the National Museum is from the Balcombian of Clifton Bank, Muddy Creek, near Hamilton. Victoria, and measures only 52.5 mm., whilst its greatest apical width is 35.5 mm ⁽³⁾.

There is a tendency in this cone for the form of the shell to become irregular or even elliptical in cross section, whilst C. pullulescens remains fairly constant in its spiral growth ⁽³⁾.

Conus dennanti

N. 1408037 - 61589

Museum Victoria

The largest specimen of C. dennanti in the Dennant collection at the National Museum is from the Balcombian of Clifton Bank (Middle Miocene), Muddy Creek, near Hamilton, Victoria, and measures only 52,5 mm ⁽³⁾