108 BRITISH FOSSIL REPTILES. 



length. 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 (z) continues long and slender 

 throughout this series. The neural spines progressively narrow and shorten, 

 with a backward inclination. The base of the haemal spine (h) of the sixteenth 

 caudal measures 9 lines ; its articular surface is transversely oblong. The surface 

 for the articulation 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, h. The 

 hgemal arch and spine becomes reduced in the eighteenth caudal to the length 

 of its centrum ; and in 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., fig. 1,23,^). The transverse diameter of the anterior 

 articular surface of the nineteenth caudal is 1 inch 6 Unes. The middle of the 

 centrum has been reduced by pressure, attended vnth 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 PI. 66, fig. 2, making us 

 acquainted with a total of thirty-five caudal vertebrae of Scelidosaurus. In the 

 last of this series the centrum (ib., 35) is reduced to the length of 1 inch, and the 

 breadth of its fi-ont articular end to 6 lines. In the twenty- fifth caudal vertebra 

 the ceuti'um (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 {h), 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, compressed ridge projecting above the part clasped by the 

 prezygapophyses. The haemal arch of the twenty-fourth caudal (ib., fig. 2, 24, 7;) 

 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; its presents a sub-bilobed 

 form, concave transversely, convex from before backward. At the sides of the 

 hsemal canal or rather slit, the arch has a fore-and-aft breadth of 4 lines ; the 



