In every conchologist’s collection will be found some of the mitre shells, so called from their resemblance to a bishop’s mitre, and principally obtained from Indian and Australian seas. So, again, the _Voluta_, with their oval and graceful forms. The animal inhabiting the latter has a very large head, provided with two tentacles and a mouth furnished with hooked teeth. The foot is very large and projects from the whole mouth of the shell, which is often ornamented with gay colours and varied marks and flutings. So also the _Conus_ genus, the title of which sufficiently indicates its general form, and some of the shells of which command high prices. These generally tropical shells are more uniform in shape than many just mentioned, but they are most beautifully varied in colour and minor details. The “residents” have large heads with _snouts_, while their mouths are furnished with horny teeth. Every good collection, too, is sure to contain examples of the genus _Cassis_, principally from the Indian Ocean. [Illustration: VOLUTA.] [Illustration: CONUS.] Among the one‐shell molluscs the Purpuras bear an honoured name; for did they not furnish the Greeks and Romans with the brilliant purple colouring matter which was reserved for the mantles of princes and patricians! The genus _Purpura_ is characterised as possessing an oval shell, thick pointed. The animal itself has a large head, furnished with two swollen conical tentacles close together, and bearing an eye towards the middle of their external side. By means of a large foot they creep about in pursuit of bivalves. The larger and more important kinds come from the warmer seas, especially those surrounding the West Indies and Australia. The purple mentioned in the Scriptures in connection with fine linen was that of the Phœnicians, and came from Tyre. Sir William Wilde discovered not far from the ruins of that city several circular excavations in a rocky cliff, and in these he found a great number of crushed and broken shells of Purpura. He believed that they had been bruised in great masses by the Tyrian workmen for the manufacture of the dye. Shells of the same species (_Murex trunculus_) are commonly found on the same coast at the present day. Aristotle says that the Tyrian dye was taken from two molluscs inhabiting the Phœnician coasts and seas. According to the great Greek philosopher, one of these had a very large shell, consisting of seven turns of the spire, studded with spines, and terminating in a strong beak; the other had a much smaller shell. It is thought that the latter is to be found in the _Purpura lapillus_, which abounds in the English Channel. Reaumur and Duhamel both obtained a purple colour from it, which they applied as a dye, and found permanent. The real secret of the production of the Tyrian purple remains undiscovered to‐day. [Illustration: PURPURA LAPILLUS.]