ICHTHYOSAURUS. 
185 
introduced for the purpose of giving rapid mo- 
tion in the water to a Lizard inhabiting the ele- 
ment of fishes ; so the further adoption of a 
structure in the legs, resembling the paddles of 
n Whale, was superadded in order to convert 
these extremities into powerful fins. The still 
further addition of a furcula and clavicles, like 
those of the Ornithorhynchus, offers a third and 
not less striking example of selection of contri- 
vances, to enable animals of one class to live in 
the element of another class. 
If the laws of co-existence are less rigidly 
maintained in the Ichthyosaurus, than in other 
extinct creatures which we discover amid the 
■wreck of former creations, still these deviations 
nre so far from being fortuitous, or evidencing 
imperfection ; that they present examples of 
perfect appointment and judicious choice, per- 
vading and regulating even the most appa- 
rently anomalous aberrations. 
Having the vertebra* of a fish, as instru- 
ments of rapid progression ; and the paddles of 
a Whale, and sternum of an Ornithorhynchus, 
as instruments of elevation and depression ; the 
reptile Ichthyosaurus united in itself a combi- 
nation of mechanical contrivances, which are 
now distributed among three distinct classes of 
the animal kingdom. If, for the purpose of 
producing vertical movements in the water, the 
sternum of the living Ornithorhynchus assumes 
