ON THE FOSSIL ICHTHYOSAURUS. 235 



layers of limestone, increasing in hardness and crystallization, from 

 hardened clay on the surface to perfect marble at the centre. When 

 brought to Birmingham, a stone-mason was employed to chip off 

 the stone from one side, so as to bring the enclosed skeleton into 

 view ; and then it was discovered that portions of the paddles, and 

 the extremities of some of the ribs were wanting, in consequence 

 of their passing quite through the stone. Mutilated, however, as it 

 is, it is one of the most perfect specimens of the Ichthyosaurus as yet 

 discovered, and is a very valuable addition to the collection of the 

 Institution. 



As now displayed, the animal is lying on its right side, with the 

 paddles extended laterally, and the head, dislocated from the neck, 

 resting on its upper part. But the description of the injuries 

 it has sustained is better reserved for the place where we shall at- 

 tempt to explain their cause ; at present our object is to describe 

 the peculiarities of the structure of this class of animals by their 

 analogies among still existing races. In external form the Ichthy- 

 osaurus partook of the appearance of the Crocodile and Lizard tribes 

 and of the Whale ; of the former in the shape of the head, body, 

 and tail, and of the latter in the form of its anterior paddles, that 

 closely resemble the fins of the Whale, and in the want of scales or 

 any external bony defence. But in imposing the name Ichthyosau- 

 rus, or Fish-Lizard, ]\Ir. Kcenig seems to have fixed his attention 

 upon the form of the vertebrae, which closely resemble those of the 

 fishes. In size the Ichthyosaurus far exceeded the recent Croco- 

 diles, being sometimes thirty or forty feet in length, of which the 

 head forms a very variable proportion, from the difference in the 

 length of the jaws in different species. 



Dr. Buckland, in his Bridgewater Treatise, has given a plate 

 of the petrified skin of the animal ; but though we have not 

 been able to discover any thing exactly similar in the present 

 specimen, yet there is a thin film of carbonaceous matter that 

 pervades the stone in such situations as we should expect to 

 find traces of this membrane. Between the ribs a large sur- 

 face of some thickness of this matter is apparent, having a la- 

 mellar and crystalline structure, that we may, with some reason, 

 conceive to be the remains of the flesh and viscera. There is also a 

 white calcareous substance lying upon the ribs, on their abdominal 

 surface, and near the carbonaceous matter last described, that, with 

 still more probability, may be referred to the excrements, which, 

 consisting chiefly of the indigestible portions of the bones of the fish- 

 es and other matters that served for its food, would not be unlikely to 



VOL. VII., NO. XXII. HH 



