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. l,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, /z) has a basal diameter of 1 inch 1 line, decreasing to G lines at the end 
of the neural canal, and thence to a terminal diameter of 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,^) have 
their articular surface turned more inward, and grasp, as it were, the shortening 
rudiments of the post-Z3?gapophyses, the neural arch progressively contracting in 
breadth. The collective length of the five vertebrae 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 Poikilopleii7'on, 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, ii), the prezygapophysis 
(ib.,fig. 4, A 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., /«) 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, a) 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. 
