10 
FOSSIL REPTILIA OF THE 
The transverse process has subsided to a tubercle upon the eighteenth (ib., 
fig. 1, d), and the postzygapophysis to a notch at the back part of the base of the 
neural spine, but the prezygapophysis {s) continues long and slender throughout 
this series. The neural spines progressively narrow and shorten, with a backward 
inclination. The base of the haemal spine (a) of the sixteenth caudal measures 
9 lines ; its articular surface is transversely oblong. The surface for the arti- 
culation of the haemal arch, from this part of the tail onward, is chiefly afforded 
by the hinder and under part of its own vertebra, as in fig. 3, a. The haemal arch 
and spine becomes reduced in the eighteenth caudal to the length of its centrum ; 
and ill the twenty-third becomes shorter than the centrum, with a greater degree 
of antero-posterior expansion of the spine in proportion to the length of that part 
(ib., fi g. 1, 23, a)- The transverse diameter of the anterior articular surface of the 
nineteenth caudal is 1 inch 6 lines. The middle of the centrum has been reduced 
by pressure, attended with some fracture of the outer surface, to a diameter of 7 
lines. In some of these vertebrae the middle, crushed parts of the centrum have 
been severed from the terminal articular expansions. I conclude, therefore, that 
they have been subjected to a general compressive force, probably connected with 
the change in the vertical relative position of the stratum. The compact layer of 
osseous tissue forming the articular end has resisted the pressure ; the intervening, 
intermediate, cancellous structure has yielded to it. 
From three smaller portions of the matrix, succeeding the ninth block, eleven 
consecutive caudal vertebrae were wrought out, as in Tab. IX, fig. 2, making us 
acquainted with a total of thirty -five caudal vertebrm of Scelidosauriis. In the last 
of this series the centrum (ib., 35 ) is reduced to the length of 1 inch, and the breadth 
of its front articular end to 6 lines. In the twenty-fifth caudal vertebra the centrum 
(ib., fig. 3) is 1 inch 10| lines in length, 1 inch 3 lines across the articular end, 7|- 
lines across the middle, the longitudinal concavity of the sides exceeding that of 
the under surface. At the fore part of this surface the hsemapophysial articulation 
is barely indicated ; at the back part it is marked by two surfaces ( A ), towards the 
most prominent part of which short, low ridges diverge. The low neural arch 
has coalesced with the upper three fourths of the centrum ; the prezygapophyses 
{z) overhang the free fore part of the centrum, and extend beyond it to clasp 
the back part of the preposed neural spine. This is represented by a short, com- 
pressed ridge projecting above the part clasped by the prezygapophyses. The 
haemal arch of the twenty-fourth caudal (ib., fig. 2, 24, A) underlies the centrum of 
the twenty-fifth ; it presents a length of 1 inch 6 lines. Its closed base (ib., fig. 4) 
has a breadth of 7^ lines; it presents a sub-bilobed form, concave transversely, 
convex from before backward. At the sides of the haemal canal or rather slit, the 
arch has a fore-and-aft breadth of 4 lines, the spine expands to twice that extent, 
with an obtusely rounded termination. In the twenty-seventh caudal vertebra 
