Amateurs must learn for themselves what these really are, and how to judge of them scientifically, when they pick up a fossil weighing, perhaps, a pound avoirdupois, and looking like a champion-potato. One or two hints may be ventured. If the creature was an “alcyonite,” its _facsimile_ in stone should have the external rings or mouths clearly defined, and, if possible, equi-distant. Such a one, when cut, will exhibit its tubes evenly disposed—not unlike a section of fir-wood under the microscope. If it was an “actinia,” then the body of the zoophyte should be central in the pebble, and the tentacles will be not much melted away in a good slice. “Sponges” must be chosen principally for their colour; in other words, for the _texture_ of the stone. Those which exhibit the reticulations, white or straw-colour, upon a very dark ground, are the most effective generally: but the most perfect one I ever saw had a blood-red pattern upon white. For a single _slice_ from this stone, half a guinea was offered by me, and refused. “Choanites” are easily discerned. The “ventriculite” must have been a creature lower down in that scale than the choanite. This fossil is repeatedly met with on our coast, but I do not admire it enough to have retained a single specimen. When alive, it would appear to have resembled, in stature and configuration, an ordinary toadstool. [Illustration: VENTRICULITE. CHOANITE.] The choanite was, undoubtedly, a beautiful creature, and, as ten thousand of the family testify, abundant. Dr. Mantell said that its form, when complete, was that of a pear or fig, and I think he obtained such a fossil from the Lewes chalk, where it was growing upright on a stalk, in the way in which he afterwards depicted it. Looking over my collection, I see that I have a similar one, in black chalcedony-flint, which I picked up at Shanklin; only, in my specimen, which came from the beach, the delicate stem is, of course, gone. The complete pyriform mound is rare, for obvious reasons. I never saw but three instances of it; the above, of my own finding, was one. Another was in pellucid white agate, spotted all over with the ends of the feelers. The third, which I also picked up, had been pounded on a rough beach, and crumbled in my hand. Choanites and ventriculites, as animals, are supposed to be extinct. Perhaps they are so, though I do not see how any one can take upon him to pronounce as to what living organisms the great Southern Ocean may or may not contain.