By Arthur de Carle Sowerby, r.z.5.
One of the most interesting branches of marine life is that of the Orustacea. is class of arthropods (animals with jointed legs) is a very old one, dating back in geologic times to the Lower Cambrian epoch. Fossil crust-oceans, in the form of trilobites. are found in some of our very oldest sedimentary rocks, or, rather. one should say, some of our' very oldest known fossils are trilobites. These were a form of crustacean not met'lwith in a living state today: they died out in the Carboniferous epoch, when the great coalfields of to-day existed as forests jand were in the making. Side by side with the later trilobites, and developing from them, were the ancestors of our, modern crustaceans. They were, apparently, all marine, and to this day the group is most strongly represented in the oceans of the world, though numerous forms have invaded fresh water and even dry land. Out of the early crustaceans developed the insects, but that is another story, as Kipling says, and does not concern us here.
Trilobites were segmented crust-oceans with numerous legs, and their chief characteristic, and the one from which the whole group derives its name, was that the body was divided longitudinally into three lobes by two grooves running from head to tail down either side of the back. They reached a high state of specialization and their zenith, so to speak, was attained in what is known as the Ordovician epoch. Numerous forms have been found in the rocks of China, one of the most interesting of which is known as the bat, or swallow, fossil. In this form the "'tail-fan" is enormously and peculiarly developed, bearing an extraordinary resemblance to the conventional Chinese pictorial representations of the bat. A slab of rock containing these fossils appears almost as though it had been decorated with the "bat" design by some Chinese artist. One of the commonest of the "bat" trilobites is known to science under the name Drepanura premesnili, and it dates from the Middle Cambrian epoch.
Text read from the printed page and cleaned; old type leaves the occasional error.