CLEODORA.
The genus Harpa includes some beautifully marked and coloured shells, of which H. ventricosa is an attractive example. These are chiefly found in the Indian Ocean. The Rock Shells (Murex) abound in every sea, but are finer and more branching in the warmer ones. They are remarkable for bright colours and fantastic forms. The shell is oblong with a long spire attached, its surface often covered with rows of branching spines. The genus Triton, of which about one hundred species are known, is ranged with the genus Murex, on account of points of similarity. The Marine Trumpet (Triton variegatum) which sometimes attains a length of sixteen inches, is a fine example. The genus Strombus includes among its species the great roughly ornamental shells, often used for grottoes or rockeries. Some of the streets of Vera Cruz are said to be paved with them. Oddest and most remarkable of all the marine shells to be found in the naturalist’s collection are those of the genus Pteroceras. They are of fresh and brilliantly shaded colours.
STROMBUS.
TRITON.
And now to the Pteropoda, practically “winged feet” molluscs, the position of which in scientific nomenclature many think unsatisfactory. This is, however, of little consequence to the general reader. These curious little molluscs can pass through the deep blue seas they usually inhabit rapidly, reminding us strongly of the movements of a butterfly or some other winged insect. They can “ascend to the surface very suddenly, turn themselves in a determinate space, or rather swim without appearing to change their place, while sustaining themselves at the same height.” “If,” continues Figuier, “anything alarms them, they fold up their flappers and descend to such a depth in their watery world as will give them the security they seek. Thus they pass their lives in the open sea far from any other shelter except that yielded by the gulf weed and other algæ. In appearance and habits these small and sometimes microscopic creatures resemble the fry of some other forms of mollusca. They literally swarm both in tropical and arctic seas; and are sometimes so numerous as to colour the ocean for leagues. They are the principal food of whales and sea-birds in high latitudes, rarely approaching the coast. Only one or two species have been accidentally taken on our shores, and those evidently driven thither by currents into which they have been entangled, or by tempests which have stirred the waters with a power beyond theirs. Dr. Leach states that in 1811, during a tour to the Orkneys, he observed on the rocks of the Isle of Staffa several mutilated specimens of Clio borealis. Some days after, having borrowed a large shrimp net, and rowing along the coast of Mull, when the sea, which had been extremely stormy, had become calm, he succeeded in catching one alive, which is now in the British Museum.” Professor Huxley has told us that they have auditory organs, are sensible of light and heat, and probably of odours, but that they possess very imperfect eyes and tentacles. They have respiratory organs, hearts and livers, and are undeniably social and gregarious, swarming together in great numbers.
We now approach the highest class of the mollusca—on paper, only, be it observed, for in actual life most of them are either nearly unapproachable, or, at all events, are most undesirable acquaintances.
“The cephalopodous molluscs,” says Figuier, a writer who in descriptive powers is an artistic scientist and a scientific artist, “are indeed highly organised for molluscs, for they possess in a high degree the sense of sight, hearing, and touch. They appear with the earlier animals which present themselves on the earth, and they are numerous even now, although they are far from playing the important part that was assigned to them in the early ages of organic life upon our planet. The Ammonites and Belemnites existed by thousands among the beings which peopled the seas during the secondary epoch in the history of the globe.” The Cephalopods were divided by Professor Owen into two great orders, Tetrabranchiata, or animals having four gills, and the Dibranchiata, having two gills. The first order has at this epoch but one genus, that of Nautilus. This group of animals belongs emphatically to the earlier ages of our globe, “is becoming gradually extinct, and presents in our days only some species very rare and few, especially when we compare them with the prodigious numbers of these beings which animated the seas of the ancient world.” It is a fact that the empty shells of the nautilus are more commonly found floating on the ocean than those which are inhabited. No doubt the living nautilus falls a prey either to larger marine animals, or, likely enough, to sea-fowl. Is it not also possible that the lone animal, knowing the fate of its ancestors, and how they lie buried in barren strata, overwhelmed with melancholy apprehensions of his own future, jumps overboard and drowns himself? This suggestion is not to be found among the recognised authorities.
On the sea this scion of a decayed family is a graceful object, and in fine weather projects his head and tentacles, and takes a general inspection of the ocean. On land, however, he does not shine to so much advantage, for there he has to drag himself over the ground, head down and body and shell up. The shell has a regularly convoluted form, and is divided into cells; doubtless this it was that gave the idea to the inventor of water-tight compartments. Through these passes a tube for respiration. In the outermost partition is the owner of the ship, covered by its mantle as a captain would be with pea-jacket or sou’-wester. The animal possesses numerous tentacles, and has two great eyes, enabling it to keep a good “look-out.”