The earliest figures of the common, or olivaceous kind, occurs in the work of Chemnitz, and among the plates of Martin. Gmelin quotes the former, and describes the shell under the name of Trochus Imperialis. It is truly a Trochus of the Linnæan classification, but not, it appears, of any later writer, excepting those of the Linnæan school. Sometimes it has been generically classed as a species of SOLARIUM, a name assigned by Lamarck to the Trochi possessing the character of the Linnæan _Trochus Perspectivus_, and which he renders into his own language as a generical epithet, by the name _Cadran_ (Sun dial). To accord exactly with the genus Solarium, as laid down by Lamarck himself, the general figure of the shell should be that of a depressed cone, having at the base an umblical opening, crenulated upon the inner edge of all the spires; as may be perceived in looking down the umbilical opening of Trochus perspectivus; and finally, the opening of the mouth should be almost quadrangular. This is the character of SOLARIUM, as proposed by Lamarck, and which does not agree exactly with the shell before us.[9] Denys de Montfort constitutes another genus of this shell, which he denominates IMPERATOR (_Conchyliologie Systematique T. 2. p. 199_) in the French, L’EMPEREUR. The olivaceous kind he calls Imperator aureolatus, l’Empereur couronné. The character of this new genus, Imperator, consists in the shell having a regular spire: in being imbricated, or covered with scales, like tiling upon the roof of a house: the carina of the whorls armed; the armament, for example, in the shell before us, consisting of a kind of frieze or curled foliage-like plates which succeed each other with great regularity: it has an umbilicus, which, in the present shell is large and deep; the mouth of the shell angular and entire; pillar lip spreading somewhat like a fan; and the exterior lip cut off. We have deemed it requisite to advert to these new genera, but as the shell itself is so clearly a Trochus, we have not thought it necessary to remove it from the place in the Linnæan System to which Gmelin had assigned. ----- Footnote 7: This article is thus described in the last day’s sale, lot 81, “An elegant and unique pink variety of the imperial sun, drawn up with the anchor of a ship, from the depth of sixty fathoms, in Cook’s Straits, New Zealand.” Sold for £24 3s. Footnote 8: In Orchard-street, Portman-square, Thursday, April 13th, 1815. _Vide_ lot 84. Footnote 9: _Système des animaux sans vertèbres, p. 86._ ------------------------------------------------------------------------ [Illustration: _12_ _London. Published as the Act directs, by E. Donovan & Mess.^{rs} Simpkins & Marshall July 1, 1822._ ] ------------------------------------------------------------------------ ENTOMOLOGY. PLATE XII.