LOWER LIAS. 9 



size of their diverging parts. The neural spine, in the ninth, is reduced to 2 inches 

 5 lines in length ; the transverse process (ib., fig. 1, d) to 1 inch 3 lines. The haemal 

 arch and spine retain a length of 3 inches 3 lines. That of the seventh vertebra 

 (fig. 1, h) has a basal diameter of 1 inch 1 line, decreasing to 6 lines at the end 

 of the neural canal, and thence to a terminal diameter of 2| lines, the fore-and-aft 

 diameter being here 10 lines. The centrums progressively become more concave 

 and compressed between the articular ends. The prezygapophyses (ib., fig. 2,s) have 

 their articular surface turned more inward, and grasp, as it were, the shortening 

 rudiments of the post-zygapophyses, the neural arch progressively contracting in 

 breadth. The collective length of the five vertebras in this block is 11 inches. 



The ninth block of Lias contains the five succeeding caudals (Tab. VIII, fig. 3). 

 The centrums, exposed at their under and lateral parts, are singularly crushed, the 

 sides of each having been pressed into the substance; yet, where the cracks of the 

 matrix expose the texture of the centrum, as in the fifteenth caudal (Tab. V, 

 fig. 3), it shows a fine, compactly cancellous structure throughout ; there is no 

 trace of any such vacuity or unossified nucleus of the centrum as is met with in 

 the vertebrae of Poikiloplenron, for example. The centrums retain their length 

 of 2 inches. The hinder articular end of that of the tenth caudal (c) adheres to 

 the fore part of the present block. In the next coarticulated vertebra, which 

 is the eleventh of the caudal series (Tab. VIII, fig. 3, n), the prezygapophysis 

 (ib., fig. 4, z ) is 10 lines in length and 3 lines in breadth ; the neural spine, measured 

 from the base of the zygapophysis, is 2 inches in length ; the transverse process 

 (fig. 3, d) is 1 inch in length, with half an inch of basal breadth. Nearly 2\ inches 

 of the haemal arch (ib., h) are preserved. 



The pressure crushing the centrum of the eleventh vertebra has been applied 

 to the middle of the under and lateral part ; the articular ends have withstood, if 

 they have received, it. The same is the case with the twelfth caudal. In the thir- 

 teenth the pressure has been more laterally applied, and the outer wall, which has 

 been driven in, preserves its vertical convexity. The diapophysis of this vertebra 

 is 10 lines in length. In the fifteenth caudal (ib., 15, d) the diapophysis is reduced 

 to 6 lines in length, with corresponding decrease of thickness. The five caudal 

 vertebrae from the eleventh to the fifteenth inclusive occupy a longitudinal extent 

 of 1 1 inches 6 lines. 



The tenth mass of Lias, fitting on to the foregoing, includes a consecutive 

 series of nine vertebrae, viz., the sixteenth to the twenty-fourth caudal inclusive 

 (Tab. IX, fig. 1). In this series there has been a dislocation of the eighteenth 

 from the nineteenth, and a similar one between the twenty-first and the twenty- 

 second vertebrae, with an interval of nearly an inch between the separated articular 

 ends of the centrums. These elements continue to decrease in vertical and 

 transverse diameters, and also, but in a minor degree, in regard to their length. 



