ON THE FOSSIL ICHTHYOSAURUS. 237 



the jaws and teeth indicate great strength and voracious habits, yet 

 this voracity must have been confined in its exercise to preying upon 

 marine animals ; for the remarkable flexibility of the skeleton of its 

 body deprived it of the power of moving upon land, except in a very 

 limited degree. First, the head was fixed to the neck by a ball and 

 socket joint, the most movable of all articulations; next, the verte- 

 bra, or joints of the back bone, were from forty to fifty in number, 

 and instead of being connected together by broad flat surfaces, as in 

 land animals, only touched at their edges, like those of fishes ; and 

 the spinous processes, instead of forming a single piece with each 

 vertebra, were jointed by their bifid roots into two holes, one on 

 each side of the groove down which the spinal marrow ran. The 

 paddles, also, consisting of numerous flat polygonal bones, ranged in 

 a tesselated manner, were quite inadequate to the support of the 

 Ichthyosaurus on land, though most powerful organs of motion in 

 the water. 



The ribs, equal in number to the vertebrae of the body, extended 

 from the head to the pelvis, as in certain Lizards ; and about twenty 

 of the upper ones were lengthened by what Mr. Conybeare terms 

 the sterno-costal arcs, which were a set of bones, five in number, at- 

 tached to each pair of ribs, that, in a manner resembling the stretch- 

 ers of an umbrella, enabled the animal to extend and contract the 

 dimensions of its chest to a degree to which we see nothing analogous 

 among existing races of animals. In the Crocodile, however, whose 

 sternum is prolonged to the pelvis, there is a set of intermediate 

 bones, between the true ribs and their cartilages, that are connected 

 to the sternum, which probably answer the same purpose. 



The Ornithorliynchus, while seeking its food among the weeds at 

 the bottom of the streams in which it dwells, is frequently obliged 

 to rise to the surface to respire : it also burrows in the banks, like a 

 Water Rat ; and hence, in order to increase the strength and elas- 

 ticity of its fore legs, a bone, similar in form and function to the 

 furcula or merry-thought of birds, is introduced between the breast 

 and shoulder bones, to which it forms a most elastic point d'appui, 

 while it keeps them apart, and antagonizes the powerful mus- 

 cles that move the anterior extremities. Sir E. Home, in his Lec- 

 tures on Comparative Anatomij, has given a representation, which 

 Dr. Buckland, in his Bridgewater Treatise, has copied, of this pecu- 

 liarity both in the Ornithorhynchus and Ichthyosaurus : but in the 

 specimen we are describing, the flat central portion of the furcula is 

 wanting, which arises, probably, from the bone having retained its 

 cartilaginous state at the time of the animal's death— a supposition 



