Geological Jlge of Reptiles, 361 



had a large head, enormous eyes, a short neck, and very long tail ; 

 it was furnished with four broad and flat paddles, and was evidently 

 destined to live in the sea ; it sometimes attained a length of from 

 twenty to thirty feet. The Plesiosaurus, which in some respects re- 

 sembled the Ichthyosaurus, being also furnished with four paddles, 

 but is yet more nearly allied to the Saurians, differs, however, from 

 it, and from all other animals, by the extreme length of the neck, 

 and the great number of cervical vertebrae. The neck of reptiles is 

 in general composed of from three to eight cervical vertebrae ; and 

 even birds (which have the maximum) have but from nine to twenty 

 three ; while one species of Plesiosaurus (P. dolichodeirus) has thir- 

 ty vertebrae. This extraordinary creature, unhke the Ichthyosaurus, 

 appears to have been but litde calculated to make rapid progress 

 through the sea, and was still less fitted for progressive motion on the 

 land ; it is therefore probable that it swam on or near the surface of 

 the water, carrying its neck like a swan, and darting on its prey, its 

 food consisting of fishes, cuttle-fish, Uc. Contemporary with the ani- 

 mals above mentioned, were several herbivorous reptiles, whose re- 

 mains have been found in the lias at Boll, in Wurtemburg, also a spe- 

 cies of crocodile ; and at Guildorf, a salamander of enormous size. 

 The remains of tortoises and turtles occur also, but very sparingly, 

 although, from the foot-marks observable in the red sandstone at 

 Corn Cockle Muir, in Dumfriesshire, this family of reptiles must 

 have existed at a still earlier period. In this bed also, several spe- 

 cies of the Pterodactylus, or flying reptile, first make their appear- 

 ance ; animals which, with the wings of a bat, and the structure of 

 a reptile, had jaws furnished with sharp teeth, and claws with long 

 hooked nails. 



The entire series of deposites composing the oolite formation, of 

 which the Has is the inferior, or lower member, abounds vi^ith the re- 

 mains of the animals of this order, and these are associated with vast 

 quantities of marine shells, principally belonging to the ancient mul- 

 tilocular genera, namely, Ammonites, Nautilites, Belemnites, &;c. 

 the whole formation having manifestly been deposited by an ocean. 

 The only apparent exceptions to this conclusion are the Stonesfield 

 beds, composed of thin strata of calcareous sandy slate, which occur 

 in the lower division of the oolite, and contain not only marine plants, 

 shells, and bones of reptiles, but also the outer cases or elytra of 

 winged insects, and jaws of animals allied to the opossum, [Didel- 

 phis.) The occurrence of terrestrial mammalia in beds of this an- 



VoL. XXL— No 2. 46 



