230
.
THE BIOLOGY OF FISHES
under the Snout and seems to have been
From this form or a form like it came, it is believed,
modern Sturgeons , which have adapted themselves to a more [ à ÊÎ
_
or less sedentary life, feeding on the bottom, with the osseousî
skeleton largely replaced by cartilage. including Polyodon
ï !
their range extends across the whole of the northern henri—’
sphere, from China to the western States of America.
: 5*_
chief centres, however, are Eastern Europe, the Caspian and
Black Sea, and the rivers owing into these seas, and iri
.
the rivers of the Great Lakes of North America.
They
,
.”
have been shut off there by changes in the land elevations,
but they retain the habit of descending periodically to the
lakes or seas.
One species, the common sturgeon (Acipens'er
55.—=Chondrosteus aCipenseroides.
Perhaps an ancestor of ..
the Sturgeon. (From Bridge,
Woodward.)
Ï
Sturio), belongs to the central or Atlantic area, where it haSj . '
kept
in touch “With both ooasts.
Thoughfalmost
»
-
,
ofrecent years,_itWas,formerlyabundant in the Rhine and
..
;
.
Medlterranean as Ïwellas
of the United îï
States
,,
; :
—
'
_
Çj -:'
fÏ
The Polyodonfannly is
—
at .” the present day ' _Î
one hand and in the
M1SSISSlPP13nd“S tr1butar1es1nthe States There also
=an9fhér oldrehctperslstsmAnnathe Bow—Fin, which, ia};
:
_
gilfive$ 'ijthe'
î;
'
AmelcaRepresntaüVesOfA1maoccurmthé —f1atef
5:_… Ï
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