266 THE LIVING ANIMALS OF THE WORLD 



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Thus h Siholmtii Phttp. Ci.'] 



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BICHIR 



IVotr the remarkable Jirileti on the hack art J ihe peculiar structure of the breast-Jins 



of the air-bladder. But 

 the best-flavoured flesh 

 and the finest caviare are 

 obtained from a compara- 

 tively small form, the 

 Sterlet, a species whicii 

 does not exceed a yard in 

 length. It is common in 

 the Black and Caspian 

 Seas, the Siberian rivers, 

 and the Danube as far as 

 Vienna. 



With the Sturgeons 

 we come to the end of 

 the Fan-finned Fishes. 

 The Fringe-finned group 

 are represented to-day 

 only by the BiCHlR and the Reed-FISH. These arc extremely interesting forms, if only 

 because they are the sole survivors of a once numerous tribe, the remains of which occur 

 as fossils in some of the oldest geological formations. They are known as Fringe-finned 

 on account of the fact that the rays which support the fin-membrane in the paired fins are 

 ranged round a lobe-shaped base, instead of running directl)- backwards to the body. As in 

 the bony pike, the body is clothed externally by large quadrangular bony plates of considerable 

 thickness, and coated with a layer of enamel. 



The BlCHiR, which is found in the Nile and other tropical rivers of Africa, is easily 

 recognised by the peculiar structure of the back-fin, which takes the form of a series of detached 

 finlets, varying in number from eight to eighteen. The length attained by the bichir is 

 about 4 feet. Gill-breathing is supplemented by the air-bladder, which is used as a respiratory 

 organ, the expired air escaping by a slit, known as the " spiracle." The young bichir breathes, 

 like a tadpole, by means of large external gills, projecting backwards on each side of the 

 head ; later these are replaced by the more efficiently protected internal gills. 



The only surviving relative of the bichir is the Reed-FISH of Old Calabar, which differs 

 by its eel-like form and the absence of the hinder paired fins. 



CHAPTER XVI 



SHARKS JXD RATS 



3V F. G. AFLALO, F.Z.S. 



TWO prevalent errors with reference to sharks continually recur in England. The first 

 is local, and has reference to the absence of " proper " sharks, whatever that may 

 mean, from British waters. The second, of wider application, holds that all sharks are 

 dangerous to man. When, some few years ago, the writer addressed a letter to the Times 

 newspaper, warning \'achting-men against summer bathing in deep water in Cornwall, a host 

 of critics accused him of a tendency to pose as an alarmist, and insisted that he was 

 confusing sharks with dog-fish. Apart from the fact that the distinction between the two 

 groups is in some cases extremely slight — it does not even rely on size, for there are dog- 

 fishes which attain to larger dimensions than the smallest sharks — these gentlemen were whollj- 

 in error, since four sharks at any rate are very common in Cornish seas, and even occur in 

 lesser numbers on other parts of the British coasts. The largest of these, the great BASKING- 



