70 
question is so scarce that the Director of the British Museum 
informs me he has not yet seen an example. Nor is the part 
figured or even mentioned in the best text-books I have searched, 
such as those of Curenu, Pictet, or QuENsTEDT’s last edition of 
the “ Petrefaktenkunde ;” so that an examination of the present 
character will have its use in directing attention to the subject. 
Fully admitting that a fanciful analogy may have misled some 
authors into a false homology of the operculum, still the subject 
is not without its special and distinct value. Even as a biological » 
element it possesses a peculiar interest, having a character 
probably of subgeneric degree in importance, and so far must 
be accorded weight as a factor in any natural system of classi- 
fication of the Mollusca. At least we would submit that, apart 
altogether from mere utility in that relation, a knowledge of 
the operculum should not be disregarded in any thorough study 
of the development and organogenesis of the order to which it 
belongs; because to such seemingly minor points the palzon- 
tologist has to defer in any sotied research into the succession, 
rank, and genetic relations of the Mollusca, whether recent or 
fossil, if his systematized knowledge would aspire to a character 
at once vital, lasting, and suggestive, to say nothing of the 
demands made on him by what we sum up in the phrase— 
scientific truth—to which may we all look with various 
energy and renewed freshness. 
THE OPERCULUM OF EHUOMPHALUS SCULPTUS, 
(OF SOWERBY.) 
PARTICULARS. 
Position Wenlock Limestone, Upper Silurian. May Hill, 
Gloucester. Found by the author in 1867. 
Description.—The operculum is shelly, ovately annular, a spiral 
of twelve whorls, the rings depressed, nodose, constricted, 
beadlike, and the substance probably horny towards the 
nucleus, which is concentric, concave within, plane without. 
Thin, with bevelled edge fitting closely into the mouth. 
