182 
MARINE SAURIANS. 
Ichthyosaurus, to he continually rising to the 
surface to breathe air* 
Here then we have a race of animals that 
became extinct at the termination of the secon- 
dary series of geological formations, presenting, 
in their structure, a series of contrivances, the 
same in principle, with those employed at the 
present day to effect a similar purpose in one 
of the most curiously constructed aquatic qua- 
drupeds of New Holland. t 
Paddles. 
In the form of its extremities, the Ichthyo- 
saurus deviates from the Lizards, and approaches 
the Whales. A large animal, moving rapidly 
through the sea, and breathing air, must have 
* In both these animals there is superadded to the ordinary 
type of bones in quadrupeds, an enlargement of the coracoid 
bone (c), and a peculiar form of sternum, resembling the fur- 
cula of birds. In PI. 12, Fig. 1, a. represents the peculiar 
sternum or furcula; b. b. the clavicles; c. c. the coracoid 
bones ; d. d. the scapulse ; e. e. the humeri ; f. g. the radius 
and ulna. At Fig 2, the same letters are attached to the cor- 
responding bones of the Ornithorhynchus. 
The united power of all these bones imparts to the chest and 
paddles peculiar strength for an unusual purpose ; not so much 
to etfect progressive motion (which, in the Ichthyosaurus, was 
produced with much greater facility and power by the tail), as to 
ascend and descend vertically in quest of air and food. 
t The Echidna, or spiny Ant-eater, of New Holland, is the 
only known laud quadruped that has a similar furcula and cla- 
vicles. As this animal feeds on Ants, and takes refuge in deep 
burrows, this structure may be subsidiary to its great power of 
digging. A cartilaginous rudiment of a furcula occurs also in the 
Dasypus ; and seems subservient to the same purpose. 
