12 FOSSIL REPTILIA OF THE 



The five sacral vertebrae are not anchylosed in a straight line, but describe a gentle 

 curve, with the concavity downwards ; the series of parapophyses, or sacral ribs, forms 

 a curved line in the opposite direction, in consequence of their different positions in the 

 several vertebrae. The summits of the anchylosed spines being truncated, describe 

 a curve almost parallel with that of the under part of the vertebrae. 



The contour of the hinder part of the body of the present gigantic carnivorous 

 Lizard, doubtless raised high above the ground upon the long and strong hind- 

 legs, must have been different from that of any existing Saurians. In these the 

 relatively shorter hind-legs, being directed more or less obliquely outwards, do not 

 raise the under surface of the abdomen from the ground ; it is the greater share 

 in the support of the trunk assigned to the hind-legs in the Megalosaur which 

 made it requisite that, as in the Iguanodon and in land mammals, a greater pro- 

 portion of the spine should be anchylosed to transfer the superincumbent weight 

 through the medium of the iliac bones upon the femora. 



In the caudal vertebrae the parapophyses are suppressed, and the single transverse 

 process is formed by the diapophysis being lengthened out by the anchylosed rudiment 

 of a rib. The haemal arch was articulated to the lower part of the vertebral inter- 

 spaces, but chiefly to the anterior vertebra. 



Bibs. Tab. IV. 



The ribs which, from their size, texture, and colour, as well as from their proximity 

 in the matrix to other more characteristic parts of the Megalosaurus, belong most 

 probably to the same species of reptile as the vertebrae above described, present a 

 double articulation with the vertebral column. 



The specimen, fig. 1, from the Stonesfield Oolite, and now preserved in the 

 Museum at Oxford, has a small, almost flattened, obtuse head, c, for articulation with 

 a parapophysis ; the neck is long, and soon begins rapidly to increase in vertical 

 thickness, being strengthened, also, by a longitudinal ridge on one side. It developes 

 a thick, obtuse tubercle, t, larger than the head, for the diapophysis. The body of the 

 rib gradually contracts, with a slight curve, to a point. The length of the body of 

 this floating rib, is little more than twice that of the neck and tubercle, showing that 

 it must have belonged to a hinder cervical or anterior dorsal vertebra. 



A second specimen, fig. 2, from the Stonesfield slate, shows a longer body, a neck 

 set on more transversely, and less expanded beneath the tubercle. The upper margin 

 of the neck is sharp ; the body of the rib is strengthened by a lateral ridge, and 

 becomes compressed in such a direction that those ridges form its margins towards the 

 lower end ; this terminates so as to indicate its having been joined to an abdominal rib. 



The upper portion of a rib from a larger specimen of Megalosaurus, and from a 

 more expanded part of the thoracic abdominal cavity, T. IV, fig. 3, formed, with 

 fig. 1, part of the original series of fossil bones, from the Stonesfield slate, de- 



