BRODIE — GEOLOGY OF GLOUCESTBllSHIRf!. 
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IHesiosaurus differed from tlie Ichthjosaurus in its long, swan-like neck.in 
its extended paddles, short tail, and small head, which it must have raised 
high above the water like a swan's ; and although a carnivorous reptile, 
it was altogether unable to cope with the Ichthyosaurus, its most dreaded 
foe. Both these genera were covered with a tough smooth skin, and 
not with scales, as we might have imagined ; and this we know from the 
discovery of a portion of the skin attached to the skeleton of an 
Ichthjosaurus, from the Lower Lias at Barrow-on-Soar, in Leicester- 
shire. 
The student must not expect to obtain a perfect specimen of one of 
these reptiles without considerable labour and perseverance ; for when 
one is found entire, much skill and patience is required to clear away 
the hard matrix which surrounds it, and many an hour has to be devoted 
to the development of even a single bone ; and some knowledge of its 
anatomy also is requisite, especially when, as it often happens, a 
specimen has been broken up into innumerable and disjointed fragment?, 
which all have to be correctly united before a full restoration of the 
original can be completed. In this way Cuvier and Owen have restored 
the entire skeleton of several extinct animals, even from heaps of bones 
piled together as in a charnel-house ; so that magically, as it were, at 
the bidding of the comparative anatomist, each bone has assumed its 
right place, and from its internal skeleton, thus remodelled, the external 
form and habits of the creature as living have been fairly demonstrated. 
It is, indeed, a wonderful power which God has thus given to man, as 
the reward of patient study and anxious thought, tlius to rebuild the 
creatures of the past. 
The strata in which these saurians are met with are not usually rich 
in other fossil remains, though the surface of the limestone is sometimes 
crowded with Ilodiola minima, and small oysters; and at Brockeridgo 
Common the blue strata are charged with Ammonites plamrlis, which 
often retains the nacreous pearly material of the shell, giving it a very 
beautiful appearance, like opal. The total thickness of this part of the 
series is about fifteen feet, having a dip of fifteen degrees to the east at 
Dcfford and at Brockeridge. The entire thickness of the Lower Lias is 
very considerable, quite six hundred feet, or even more, but much less 
in the south and south-east districts. 
We have now arrived, in descending order, at the " basement-beds'' 
of the Lias, the lowest of which rest immediately on tlie Eed Marl, 
