rLATE XL 



despoiled of its exterior coating by these attacks, as to render it 

 impossible to form any tolerable conception of the shell when perfect ; 

 even an approach towards perfection in its outer coating is very rare. 

 The most complete of its kind in the collection of the late Admiral 

 Bligh, and probably selected as the best he ever met with, wass 

 perfect in this respect than might be expected. By one of those rare 

 chances which sometimes happen, the Roseate variety, which forms 

 the subject of our present illustration, had entirely escaped every 

 accident of this nature, insomuch^ that its figure may be regarded as 

 that of a very perfect shell. 



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 Linnaean classification, but 

 not, it appears, of any later writer, excepting those of the Linnaean 

 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 Linnaean 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 

 bid 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.* Denys de 



* Si/steme des animaux sans vertebres, p. 86. 



