26 EXPLANATION OF PLATE 14. 



Lyme Regis, presented to the Oxford Museum by Viscount 

 Cole, enclosing within its ribs scales, and digested bones of 

 Fishes, in the state of Coprolite. This coprolitic mass seems 

 nearly to retain the form of the stomach of the animal, 

 c, Coracoid bone, d. Scapula, e, Humerus, f, Radius, 

 g. Ulna. (Scharf. Original.) 



Plate 14. V. I. p. 191. 

 Skeleton of the Trunk of a small Ichthyosaurus in the 



Fig. 5. Nearly flat articular surface of (probably) the third cer- 

 vical vertebra of the same large Individual as Fig. 3. This surface of 

 the bone has only a small cylindrical depression at its centre, instead 

 of the deep, conical cup of the more flexible vertebrae, C. B. E. 



Near its upper margin is a wedge-shaped elevation (b) and near 

 the inferior margin, a notch or furrow (a). These salient and re- 

 entering portions articulated with corresponding depressions and 

 projections on the surface of the adjacent vertebra, and acted as 

 pivots, admitting a limited amount of lateral vibrations, and at the 

 same time preventing any slip, or dislocation. 



Fig. 6. Concave surface of Fig. 5. ; the wedge-shaped projection 

 near its lower margin (a) must have articulated with a correspond- 

 ing groove or depression on the front of the vertebra adjacent to it, 

 like that at (Fig. 5. a.) As one surface only of these vertebrae had 

 a conical cavity, the intervertebral substance must have formed a 

 single cone, admitting in the neck but half the amount of motion, that 

 the double cones of intervertebral matter allowed to the dorsal and 

 caudal vertebrae, (C. B. E.) where greater flexure was required, to 

 effect progressive motion by vibrations of the body and tail. 



These dispositions of the articulating facets of the cervical ver- 

 tebrae, acting in conjunction with the three sub-vertebral wedges 

 before described, afford an example of peculiar provisions in the 

 neck of these gigantic Reptiles, to combine a diminished amount of 

 flexure in this part, with an increased support to their enormous 

 heads. 



It is probable that every species of Ichthyosaurus had peculiar vari- 

 ations in the details of the cervical vertebrae, and subvertebral wedges, 

 and that in each species these variations were modified by age. 



In the Gavial Mr. Mantell has recently observed that the first 

 caudal vertebra is doubly convex, like the last cervical vertebra in 

 Turtles. These peculiar contrivances give to the animals in which 

 they occur increased flexibility of the Tail and Neck. 



