A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . however,traces have not been found. The funnel is seen emerging infront of the mantle-folds, and on each side of it is an this is the body-chamber, protected on the back bythe pro-ostracum, not seen in this view. The viscera arenot shown, since nothing definite is known about them, withthe exception of a small bag, from which a tube leadsforward and opens into the funnel. This bag is filled with acarbonaceous substance which, as known in living cephalop
A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . however,traces have not been found. The funnel is seen emerging infront of the mantle-folds, and on each side of it is an this is the body-chamber, protected on the back bythe pro-ostracum, not seen in this view. The viscera arenot shown, since nothing definite is known about them, withthe exception of a small bag, from which a tube leadsforward and opens into the funnel. This bag is filled with acarbonaceous substance which, as known in living cephalopods,can be ejected in the form of a dark ink. It serves to 154 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. Gallery obscure the water and protect the animal in its flight fromaMe-case enemy. A paint made from this ink is called sepia, after1. the Latin name of the cuttle-fish. The ink-bag is oftenfound in these fossils, and its contents can still be used as apaint. Behind the body-chamber are seen the phragmoconeand the guard, and stretching along the sides of the wholeshell are expansions of the mantle, forming fins. Belemnites. Fig. 84.—Eestoration of the animal and shell of belemnites. a, backview ; b, front or under view. (After dOrbigny.) having this general structure and a solid guard lived to theclose of the Cretaceous Epoch, when they disappeared. Whereas the Ammonites left no descendants, thebelemnites appear to have become changed into other of these, Belosejoia, is found in the Eocene London ClayTable-case (Fig. 85 d). Here the guard has become reduced in size, andthe septa stretch in an upward curve from the apex of theshell (corresponding to the belemnite phragmocone) to thefront of the pro-ostracum. They are numerous and closetogether. This form leads to the ordinary Sepia or cuttle-fish, of which two glass models are shown. The shell of this MOLLUSCA—CEPHALOPODA. 155 animal is the familiar cuttle-bone (Fig. 85 e). Viewing it ^^^^from the back one sees
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