Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/138

 134 which are now dispersed through various classes and orders of existing animals, but are no longer united in the same genus. Thus, in the same individual, the snout of a Porpoise is combined with the teeth of a Crocodile, the head of a Lizard with the Vertebræ of a fish, and the sternum of an Ornithorhynchus with the paddles of a Whale. The general outline of an Ichthyosaurus must have most nearly resembled the modern Porpoise, and Grampus. It had four broad feet, or paddles, (Pl. 7,) and terminated behind in a long and powerful tail. Some of the largest of these reptiles must have exceeded thirty feet in length.

There are seven or eight known species of the genus Ichthyosaurus, all agreeing with one another in the general principles of their construction, and the possession of those peculiar organs, in which I shall endeavour to point out the presence of mechanism and contrivance, adapted to their habits and state of life. As it will be foreign to our purpose to enter on details respecting species, I shall content myself with referring to the figures of the four most common forms (Plates 7, 8, 9.)