PALEONTOLOGY. 



The JRhi/nchosaurus, from the new red-sandstone of 

 Grinshill. 



4th Family. The ICHTHYOSATJEID^. This singular family 

 is composed of large extinct marine reptiles, which had 

 structural affinities with the modern cetacea, and by which 

 a transition is made from. the reptilian to the mammalian 

 types of structure : it comprises several genera. 



The Ichthyosaurus* had the general contour of a dolphin, 

 the head of a lizard, the teeth of a crocodile, the sternal 

 arch of an ornithorhynchus, and the paddles of a whale. The 

 sclerotic coat of the eye was encircled by a series of osseous 

 plates like the sclerotic of tortoises, birds, and some saurians.f 

 The extremities are shortened, and converted into oars, and 

 Jv;r! consist of a number of small cubical bones arranged like a 

 tesselated pavement, firmly tied together by ligaments, and 

 enveloped in the common integument. Their flexible spines, 

 ^ \ powerful tails, and oar-like fins, rendered them admirably 

 adapted for an aquatic life, and the form and structure of 

 their teeth show that they were 

 carnivorous. Their intestinal canal 

 was short, like that of some fishes, 

 and was furnished with a spiral 

 valve. We form this conclusion 

 from the impression observed on 

 the surface of the coprolites, which 

 we find enclosed in their bodies, 

 and strewed among the strata with 

 their remains. We know one spe- 

 cies from the muschelkalk of Lune- 

 ville, in Germany. This genus 

 attained its greatest development 

 in the lias. The different stages 

 of the oolites contain their remains, 

 and they have been found in strata 

 of the same age in North America. 

 The Plesiosaurus had the head 

 of a lizard, the teeth of a crocodile, 

 a neck of enormous length like the 



* See the frontispiece for restored figure of this reptile. 

 *f* Dr. Wright, on the Comparative Anatomy of the Organs of Vision, Chel- 

 tenham Magazine, 1837. 



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