The
head is of enormous size, with greatly prolonged jaws, holding
numerous powerful conical teeth lodged in a common groove. The
nature of the dental apparatus is such as to leave no doubt as
to the rapacious and predatory habits of the Ichthyosaurs--an
inference which is further borne out by the examination of their
petrified droppings, which are known to geologists as "coprolites,"
and which contain numerous fragments of the bones and scales
of the Ganoid fishes which inhabited the same seas. The orbits
are of huge size; and as the eyeball was protected, like that
of birds, by a ring of bony plates in its outer coat, we even
know that the pupils of the eyes were of correspondingly large
dimensions. As these bony plates have the function of protecting
the eye from injury under sudden changes of pressure in the
surrounding medium, it has been inferred, with great probability,
that the Ichthyosaurs were in the habit of diving to considerable
depths in the sea. Some of the larger specimens of _Ichthyosaurus_
which have been discovered in the Lias indicate an animal of
from 20 to nearly 40 feet in length; and many species are known
to have existed, whilst fragmentary remains of their skeletons
are very abundant in some localities. We may therefore safely
conclude that these colossal Reptiles were amongst the most
formidable of the many tyrants of the Jurassic seas.
Pages:
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369