266 THE LIVING ANIMALS OF THE WORLD 
eases: | 
| 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 which 
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 
T Phos 9y sllonte Pinan G09 [Parson's Green we come to the end of 
BICHIR the Fan-finned Fishes. 
Note the remarkable finlets on the back and the peculiar structure of the breast-fins The Fringe-finned group 
are represented to-day 
only by the BICHIR and the REED-FISH. These are 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 directly 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 BICHIR, 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. 
poo : == LE 
CHAPTER. 2v-l 
SHARKS AND RAYS 
BY F. G. AFLALO, F.Z.S. 
WO 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 Zzmes 
newspaper, warning yachting-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 wholly 
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- 
