ICHTHYOSAURUS. 143 



at the bottom of lakes and rivers, and is obliged, like the 

 Ichthyosaurus, to be continually rising to the surface to 

 breathe air.* 



Here then we have a race of animals that became extinct 

 at the termination of the secondary series of geological for- 

 mations, presenting, in their structure, a series of contri- 

 vances, the same in principle, with those employed at the 

 present day to effect a similar purpose in one of the most 

 curiously constructed aquatic quadrupeds of New Holland.f 



Paddles: 



In the form of its extremities, the Ichthyosaurus deviates 

 from the Lizards, and approaches the Whales. A large 



a quadruped clothed with fur, having a bill like a duck, with four webbed 

 feet, suckling its young, and most properly ovoviviparous : the male is fur- 

 nished with spurs. — See Mr. tR. Owen's Papers on the Ornithorhynchus 

 Paradoxus, in the Phil. Trans. London, 1832, Part 11. and 1834, Part II. 

 See also Mr. Owen's Paper on the same subject in Trans. Zool. Soc. Lond. 

 Part III. 1835, in which he points out many approximations in the gene- 

 rative and other systems of this animal to the organization of reptiles. 



* 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 furcula of birds. In PI. 12, Fig. 1, a. re- 

 presents the peculiar sternum or furcula; b. b. the clavicles ; c. c. the cora- 

 coid bones: d. d. the scapulae; e. e. the humeri ; f. g. the radius and ulna. 

 At Fig. 2, the same letters are attached to the corresponding bones of the 

 Ornithorhynchus, 



The united power of all these bones imparts to the chest and paddles pecu- 

 liar strength for an unusual purpose ; not so much to effect progressive mo- 

 tion (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 

 land quadruped that has a similar furcula and clavicles. 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. 



