FROM THE LOWER LIAS OE CHARMOTJTH. 453 



Dorsal Series. (Plate XXIII. fig. 2.) 



The dorsal vertebrae are well exposed in a fine and complete series 

 on the underside of the specimen. They have the same general 

 character as the last two cervicals — the centrum being smooth, not 

 tuberculated, its height (d.v.) and length (a.p.) being about equal, 

 and both shorter than the breadth (1.1.). The maximum dimensions 

 of the centrum appear to be attained in the fortieth vertebra, in which 

 the length and height are each 2*8 inches, and the breadth 4*8 inches ; 

 its total height, however, is only 7*6 inches, being less than that of the 

 forty- third vertebra, which is 8*2 inches high ; behind the fortieth the 

 centra decrease in size, and a little more rapidly in breadth than in 

 the other dimensions. The transverse processes rise upon the verte- 

 brae from the thirty-ninth (xxxix) to the forty-second and forty-third 

 (xlii and xllti) beyond which they spring from the neural arch along 

 the zygapophysial line ; they maintain this position down to the fifty- 

 sixth (lvi), past which they begin to descend and also change in 

 character. At first, as in the fortieth vertebra (xl) or second dorsal, 

 the pedicel of the transverse process projects outwards at right angles 

 to the vertical plane given by the flat side of the neural spine ; 

 passing backwards this angle is much diminished, so that in the 

 forty-fourth (xliv) vertebra it is only 65° ; behind this it begins to 

 increase again, and at length becomes 90° at the fifty-fifth (lv) 

 vertebra, or seventeenth dorsal. 



The length of the transverse process increases slowly down to the 

 forty-seventh (xlvii), in which it is 4-3 inches long ; behind this it 

 slowly shortens and becomes 1*5 inch at the fifty-eighth vertebra. 



The dorso-ventral diameter of the base of the transverse process 

 is at first, as in the fortieth vertebra, 2-1 inches ; but it rapidly 

 diminishes, so that at the forty-third it has become 1*2 inch ; 

 past the forty-third it remains pretty constant as far as the fifty- 

 sixth vertebra. At the fifty-sixth important changes commence ; the 

 transverse process loses its straight boldly projecting form and droops, 

 as it were, into a curve, assuming the character of the last cervical 

 transverse process. In the fifty-eighth vertebra the facet is inclined 

 downwards and backwards ; but its form cannot be fully made out, 

 as its lower half is concealed by the head of its rib. 



The neural spines are parallel-sided, and truncated above by a 

 straight or very gently curved distal margin. They attain their 

 greatest length and breadth in the fortieth to forty-third vertebrae, 

 past which they diminish in size slowly. In the early part of the 

 dorsal region the spines are inclined backwards at a slight angle ; 

 thus in the fortieth to forty-second vertebrae the axis of the spine 

 makes with the zygapophysial line an angle of 64°, i. e. it slopes 

 backwards 36° from the vertical ; posteriorly the backward inclina- 

 tion diminishes and the spine becomes at length vertical ; this is the 

 case at the fifty-fifth vertebra ; still more posteriorly the inclination 

 becomes reversed and the spine slopes forwards ; thus in the fifty- 

 seventh vertebra it makes an angle of 93° with the zygapophysial 



Q.J.G.S. No. 147. 2h 



