Photo by W. Saville-Kent, F.Z.S.] [Milford-on-Sea.
SHELL OF THE ARGONAUT, OR PAPER-NAUTILUS.
The female animal only possesses a shell, and uses it as a cradle for her eggs and young.
The various species of Nautilus, including the so-called "Paper" and "Pearly" species, belong likewise to this group of Molluscs. In the former case, however, it is only the female animal which secretes a shell, and this is used as a cradle wherein she deposits her eggs and rears her young. The pretty romance of the Paper-nautilus, or Argonaut, as it is technically termed, floating on the sun-lit waves with spreading sails and an even keel, has unfortunately been entirely dissipated by the penetrating search-light of modern science. The animal only floats on the surface when ill, or when torn from its customary pasture-fields by abnormal storms, otherwise it creeps about the sea-bottom, or disports itself in the sub-marine grottoes like an ordinary octopus, with which, in point of fact, the shell-less male agrees in all essential details. The shell-cradle of the paper-nautilus is not vitally connected with the body of the animal, as is that of the pearly species and all ordinary shell-fish. It is freely detachable from the body, and during life is grasped and held closely to it by the expanded extremities of the two lateral tentacles by which the delicate shell is mainly secreted.
The next group comprises the great bulk of Simple-shelled Molluscs, of which it is impossible in these pages to give more than a brief enumeration of some of the most prominent. The Lung-breathing section, which is usually awarded the first place on the list, includes the familiar Garden-snails, the Shell-less Slugs, the Fresh-water Snails which come to the surface to breathe, and many distinct terrestrial species. The largest living representative of this group is the huge Land-snail of tropical West Africa, sometimes known as the Agate-snail, the shell of which is not infrequently as much as 7½ inches long.
Photos by W. Saville-Kent, F.Z.S.]
LIMPETS, WHELKS, AND BARNACLES.
On the rocks at Ilfracombe when the tide was low.