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.
The creature, however, which I admire most, as perpetuated in these marine fossils, is not a choanite, but an actinia of the “crass” kind. One of these, large and of a globular form, in which the tubular tentacles are distinctly shown, and the colour is yellow in the agate, I found, in a sequestered spot, where the deep sand must have received and sheltered it shortly after it had dropped from the cliff. The outer whitey-brown crust was unbroken: and as this crust is the cuticle of the pebble, and which always wears away first, I have no doubt of the specimen being a perfect one. It could never have undergone a rub, beyond that from soft sand or softer seaweed.
Lastly, striped jaspers and bloodstones are to be had for the seeking, on our Devonshire and Yorkshire coasts. The bloodstone is too well known to need any description; neither is there much variety or interest in a rush-green, spotted with red. But the jaspers embrace several other colours, and many lively patterns. South Devon has good ones, resembling agatized wood. Scarborough has good ones, some of them quite equal to the “weed-agate” of India. At Eastbourne, a dark-brown variety is occasionally found, which is highly prized, because it approaches the character of the Egyptian. Fine pebbles of this kind are also to be obtained in the neighbourhood of St. Alban’s, in Hertfordshire, but they are liable to be gritty.
Beside the above, which are true jaspers, scores of jasper-flints in bright red, yellow, or green, occur on almost any beach. These are simply burnt flints, containing a portion of oxide of iron. Their present condition is probably the result of extinct volcanic agency. These are not nearly so hard as the true jaspers, and their fracture is “conchoidal.”
For pleasing the eye, perhaps the choicest stone in Britain is a moss-agate, of which the pretty name yields an accurate description. The “moss” is some oxidized metal, whose ramifications form a striking contrast with the limpid chalcedony in which it seems to float like seaweed or sponge.