" As its respiratory organs were such
that it must of necessity have required to obtain air frequently,
we may conclude "that it swam upon or near the surface, arching
back its long neck like a swan, and occasionally darting it down
at the fish which happened to float within its reach. It may
perhaps have lurked in shoal water along the coast, concealed
amongst the sea-weed; and raising its nostrils to a level with
the surface from a considerable depth, may have found a secure
retreat from the assaults of powerful enemies; while the length
and flexibility of its neck may have compensated for the want
of strength in its jaws, and its incapacity for swift-motion
through the water."
About twenty species of _Plesiosaurus_ are known, ranging from
the Lias to the Chalk, and specimens have been found indicating
a length of from eighteen to twenty feet. The nearly related
"_Pliosaurs_," however, with their huge heads and short necks,
must have occasionally reached a length of at least forty feet--the
skull in some species being eight, and the paddles six or seven
feet long, whilst the teeth are a foot in length.
[Illustration: Fig. 178.--_Pterodactylus crassirostis_. From the
Lithographic Slates of Solenhofen (Middle Oolite). The figure is
"restored," and it seems certain that the restoration is incorrect
in the comparatively unimportant particular, that the hand should
consist of no more than four fingers, three short and one long,
instead of five, as represented.
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