226\ PALEONTOLOGY. 



the Ichthyosaurus. It appears to me to give additional proof 

 of the collective tendency of the affinities of the Ichthyosaurus 

 to the labyrinthodont and lacertian types of structure. The 

 backward or antorbital position of the nostrils, like that in 

 whales, is related to their marine existence. But in the Laby- 

 rinthodonts and Lacertians, the nostrils being nearer the fore 

 part of the head, their anterior boundaries are formed by the 

 premaxillaries ; it appears, therefore, to be in conformity with 

 the above-mentioned affinities, that the premaxillaries of the 

 Ichthyosaur should still enter into the same relation with the 

 nostrils, although this involves an extent of anterior develop- 

 ment proportionate to the length of the jaws, the forward pro- 

 duction of which sharp-toothed instruments fitted them, as in 

 the modern dolphins, for the prehension of agile fishes. 



That the Ichthyosaurs occasionally sought the shore, 

 crawled on the strand, and basked in the sunshine, may be 

 inferred from the bony structure connected with their fore 

 fins, which does not exist in any porpoise, dolphin, grampus, or 

 whale ; and for want of which, chiefly, those warm-blooded, 

 air-breathing, marine animals are so helpless when left high 

 and dry on the sands. The structure in question in the 

 Ichthyosaur is a strong osseous arch, inverted and spanning 

 across beneath the chest from one shoulder-joint to the other; 

 and what is most remarkable in the structure of this " scapular" 

 arch is, that it closely resembles, in the number, shape, and 

 disposition of its bones, the same part in the singular aquatic 

 mammalian quadruped of Australia, called Ornithorynchus, and 

 Platypus, or duck-mole. The Ichthyosaur, when so visiting 

 the shore either for sleep or procreation, would lie or crawl 

 prostrate, with its belly resting or dragging on the ground. 



The most extraordinary feature of the head was the enor- 

 mous magnitude of the eye : and from the quantity of light 

 admitted by the expanded pupil, it must have possessed great 

 powers of vision, especially in the dusk. It is not uncommon 



L. 



