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Show 1878.] FORMOSA AND THE PERSIAN GULF. 731 aspect of the latter, namely the moulding of the edges of the valve by the animal to the surface of the substance to which the shell is attached, no doubt, was employed by the Oyster here figured ; for I do not think that this alteration of outward appearance has been in any way effected by contact of the tentacular cirri which proceed from the edge of the mantle of the Trochus, because if this were the case some alteration in colour would have been expected. The lower valve is white both externally and within, and, being thin, does not conceal the granular surface of the Trochus upon which it rests. The upper valve is olive-green within, and smooth, with the exception of the pear-shaped muscular scar and a few small granules scattered all round the margin. The exterior is dark lilac, with six obscure brownish rays, most observable towards the margin, and terminating at the digitations or prolongations at the edge. The lamellated surface, so common to the upper valves of most Oysters, is almost altogether obliterated, and only here and there traces of it are noticeable. The exterior is rather smooth, sub-angular, the indistinct granules arranged in series corresponding to those on the Trochus; and the suture dividing the last and the penultimate whorls, and a depression or sulcus round the middle of the former, are also reproduced. The specimen is in the collection of Mr. Carl Bock. CYPRAEA PEASEI, Sowerby. (Plate XLVI. figs. 13 & 14.) Cypreea peasei, Sowerby, Thesaurus Conchyl. iv. pl. 311. figs. 167, 168. Hab. Mauritius. Coll. Carl Bock. The shell here figured appears to be a monstrous growth of this species. The alteration of form and the obtuse ridges on the dorsal surface are suggestive of certain forms of the genus Ovulum. CONUS PASTINACA. Much uncertainty and confusion exists with regard to the determination of this Lamarckian species. The original description of it is so brief that it is absolutely impossible ever to know with certainty what species Lamarck really had before him, more especially as the actual type (which has been lost) was never figured by him, nor does he refer to any previously published figure. The shell described and delineated by Kiener (Coq. Viv. pl. 26. fig. 2) certainly cannot be the true C. pastinaca. The species there represented (unknown to me) is decidedlv distinct. The character of the spire does not at all agree with Lamarck's description, which is as follows .__•< Spira obtusa, immaculata, submucronata;" and again m French : "a spire non tachee." Kiener's shell has a rather concavely elevated spire and fulvous blotches upon it. Reeve's idea of C. pastinaca, figured (Conchol. Icon. l. pl. 46. fig; 257 copied by Sowerby, Thesaurus Conchyhorum, in. pl. 201. fiS 353) from a specimen in the British Museum, is also an erroneous one This shell I have very carefully examined, and unhesi- |
