Table of Contents
"There are curious things of which men know
As yet but little.
—————————— Shells
Which ocean flingeth forth from off her billows
On the low sand.
Unfortunately for our knowledge of Conchology, collectors content themselves too frequently with gathering the dead and empty shells washed up by the 'tide, as if they, fractured, waterworn, and colourless, could give any idea of the glorious creatures which had inhabited them;—as well might they judge of a man's habits and character by walking through his house;—and it is the mere formation of cabinets for the beauty of the shells which has led to this being considered a frivolous study, and so, without knowing the habits of the animal, and its conformation, affecting the form of the shell so very materially, it is. Still collectors often hunt up objects which had escaped the eye of those more educated in scientific pursuits, so instead of criticising the past, we will rather give a brief digest of the peculiarities which characterise this division of the Natural Kingdom, as well as some few hints for the guidance of the Amateur Naturalist in his researches for the future.
Shell-fish then, be it known, belong to that division of the Natural World called "Mollusca" from the Latin word mollis (soft), their bodies consisting universally of a soft consistence and generally protected by a hard shell, Univalve or Bivalve. Taking first now the Univalves, which have a distinct head, eyes, and tentacles, the mouth being armed with jaws, we find that Cuvier has arranged them into three classes, the animals belonging to the first of which are termed Cephalopoda (from Cephale the head, and poda feet), because their feet, or rather arms, which are attached to the head form a circle around the mouth; the Cuttle fish is a familiar example, and its shell, which is internal, as in almost all comprised in this class, is constantly thrown upon our shores;—the beautiful little discoidal chambered shell of the Spirula, is not uncommon on the Warrnambool and other of our coasts, the animal itself would indeed be a prize, for although an inhabitant of all the warm seas, it is not often met with.
The animals of the second class, or Gasteropoda, of which the common garden snail is a good type, creep by the successive expansion and contraction of their broad muscular foot, which is formed by the under side of the body, and thus the name of the class is obtained from gaster, the belly, and as before poda, feet. Some breathe air, (pulmonifera), others water (branchifera.) Many of the individuals of the latter division close their habitations with a horny or calcareous covering called an operculum, and it presents strange modifications of structure; we find it in some spiral, in others concentric, and occasionally claw-shaped; that of a Natica found on the Western Coast, is commonly used as card counters, and we have seen them polished and tastefully mounted as wrist studs and shawl pins. Our shores give us many Carnivorous Gasteropods, for example, Murex; Fusus, or Spindle shell; Nassa, or Dog-whelk; Purpura, or Purple shell, (some species of which afford a dye); Conus or Cone shell; Voluta; Mitra or Mitre shell; Cypræa, (Cowrie), &c., &c. Livnigstone, in his entertaining travels tells us that the chief Shinte, as a last proof of his friendship came into his tent, which he closed to prevent the possibility of there being any witnesses to his extravagance, and then presented him with the conical end of a Cone shell, adding as he did so, "There now you have a proof of my friendship." So high a price was set on these shells, that five of them would be a handsome sum for an Elephant's tusk worth £10.
In brackish water we may find many of the Seasnails, the pretty little mottled Natica, the long spiral Cerithium, and on the rocks at Lady Bay we have seen specimens of the Siliquaria or Pod shell, which is longitudinally slit all along its twisted spire; the Litorina or Periwinkle, is always found within the action of the tide, as it feeds on sea-weed, and the brackish lagoons afford us the pretty minute Looping snail (Truncatella) in abundance, and it has one recommendation that it can survive for a considerable time in the mud, when the water has been dried up by the Summer's sun.
The richly-colored Pheasant shell (Phasianella) should be sought after eagerly on the Warrnambool and other shores, since it forms so lovely an object for the Cabinet; its generic name has its origin in the resemblance of the markings of the shell to the plumage of the Pheasant (Phasianus): the hoop shells Trochi, are found attached to rocks on all our coasts; of the Ear shells (Halotis), and Boat shells (Chiton), we shall have much to say hereafter when we meet with them.
Of the Pulmonifera or air-breathing Mollusca, some are terrestrial, others fresh-water, and many inhabit damp places near the sea; their respiratory organ is so simple a form of lung, that this order is called by Gray, "concealed lunged," as the orifice is small and valve—like to guard against the entry of water in the aquatic tribes, and to prevent the rapid desiccation in the land snails.
The latter do not abound in Australia, but we find abundant interest in the beautiful shells which exist in the Yarra, the Moorabool, the Merri, and other of our rivers, lurking on the large, ovate, floating leaves of the Nymphæa-like Damasonium, or the broad paler Potamogiton (Pond-weed), which is always so gay and refreshing an object, but these we must needs put into an Aquarium to watch with the aid of a pocket lens their structure and habits. We place along with them some of the green scum which covers the surface of the water (we say scum, but it is in reality a beautiful freshwater Alga,) a Zygnema in conjugation, and a few plants, such as Chara, the velvety Azolla rubra or pinnata, one or the other of which is to be met with on the Merri, at Warrnambool; the Moorabool, at Geelong; on the lagoon in the Botanical Gardens, Melbourne, and such like situations. The flat many-whorled shell, so brittle—is a Planorbis, this other, ovate-shaped and also very thin with a large aperture, is a Physa, so called from its resemblance to a pouch; and the one, with the aperture on the right, which distinguishes it from the former is an allied genus, Limnæa, or Pond-snail. All these are widely distributed throughout the world. Now then let us watch how industriously they are cleaning off the dark coating of Conferva, which has already commenced growing on the sides of our Aquarium, and with this lens see how they use their tongue; the upper lip with its mandible is raised, the lower lip which is horse-shoe shaped, expands, the tongue is protruded and applied to the surface for an instant, and then withdrawn; its teeth glitter like glass paper, and in Limnæa it is so flexible that frequently it will catch against projecting points, and be drawn out of shape slightly as it vibrates over the surface.[1]
Both these last species crawl beneath the surface of the water with their shells downwards, the Limnæa depositing its eggs, some fifty or sixty in number, in small sacs, and Mr. Hogg, in his valuable work on the Microscope, (Edition 4, p. 423,) gives us some interesting information on their subsequent development, " When examined soon after they are deposited, the vesicles appear to be filled with a perfectly clear fluid; at the end of twenty-four hours a very minute yellow spot, the nucleus or germ, may be seen near the side of the cell-wall. In about forty-eight hours afterwards, this small germ has a smaller central spot, rather deeper in color, which is the nucleolus. On the fourth day the nucleus has changed its position, and is enlarged to double the size upon viewing it more closely a depression or fissure is seen—this on the eight day most distinctly divides the small mass into the shell and soft part of the future animal. It is then detached from the side of the cell, and moves with a rotatory motion around the cell interior; the direction of this motion is from the right to the left, and is always increased when the sunlight falls on it. The increase is gradual up to the sixteenth day, when the spiral axis can he made out, and it presents a striking difference to the soft parts in appearance. On the eighteenth day these changes are more distinctly visible, and the ova crowd down to the mouth of the ova-sac; by using a higher magnifying power, a minute black speck, the future eye, is seen protruded with the
