CORONULA BISSEXLOBATA. De Blainville. Dict. des Sciences Naturelles, tom. 32, (1824), Tab. 117, fig. 1.
PLATYLEPAS PULCHRA. J. E. Gray (!). Annals of Philosophy, (new series), vol. 10, (1825).
COLUMELLINA BISSEXLOBATA. Bivona (fide Philippi). Nuovi generi di Mollusch. (1832), Tab. 3, fig. 1.[126]
CORONULA CALIFORNIENSIS. Chenu (!). Illust. Conch., Tab. 1, fig. 4.
[126] This memoir was published in the ‘Effemeridi Scientifiche e Litt. per la Sicilia,’ according to the ‘Bibliographia Zoologiæ et Geologiæ,’ by Agassiz and Strickland.
Shell with the transverse lines of growth conspicuous: parietes permeated by pores; sheath descending barely half-way down the parietes.
Hab.—Mediterranean, attached to turtles. River Gambia, attached to manatee. Honduras, attached to manatee. Moreton Bay, lat. 27° S., Australia, apparently attached to the dugong of that coast. California(?) Mus. Brit., Stutchbury, and Cuming.
General Appearance.—Shell generally much depressed, and broadly oval or circular; sometimes steeply conical. Orifice oval, generally not large. Surface rather plainly marked by closely approximate lines of growth, which with the lobed outline gives to the whole an elegantly sculptured appearance: occasionally the longitudinal ridges formed by the parietal septa are distinct. Basal diameter of largest specimen three quarters of an inch.
Structure of Shell.—I have nothing material to add to the generic description. The midribs are not so prominent as in the following species, and hence the basal membrane is less convex. The origin of the midrib as a fold is very plain. The sheath descends barely half-way down the walls, and is a little hollow on its under margin, on each side of the midrib. Beneath the sheath the parietes are finely ribbed (fig. [1 d]), but to a variable degree. I may here remark, that in the specimens taken from manatee, on the coast of Africa and at Honduras, the internal ribs extended further up and were plainer, and the opercular valves seemed to be a little narrower than in the other specimens, so that I at first suspected that they were specifically distinct, but I could make out no other than these small and variable points of difference.
Scuta: oblong (fig. [1 c]), about twice as long as broad, with the rostral end rounded, rather narrower than the other end, and curled a little inwards. Terga, of nearly the same shape and nearly as long as the scuta: the carinal end is rather more pointed than the scutal end of the valve, and when viewed internally, the growing surface of this end is seen to be bluntly pointed. In both valves the upper layers of shell usually scale off.