106 BRITISH FOSSIL REPTILES. 



concave, with tlie circumference bevelled off convexly ; between tbe two expanded 

 ends the centrum is moderately and uniformly concave lengthwise. There is no 

 trace of hgemal arch in the first caudal. In the second that arch fPl. 54, fig. 2 h) 

 is articulated to the posterior part of the under surface, and is produced into a 

 spine of nearly 4 inches long. In the third caudal (ib., h, c 3) and succeeding ones 

 the hgemal arch has been dislocated, showing its articular surface, which, by mutual 

 union of the hgemapophysial bases, is single, sub-reniform, transversely extended, 

 lightly concave across, and convex from above downward. The hasmal canal, thus 

 circumscribed, and well shown in the fourth caudal vertebra, is about 2 lines in 

 breadth and 1 inch 3 lines in length ; too narrow, it would seem, for the protection 

 of the trunks of the blood-vessels supplying so long and so powerful an organ as 

 the tail of the Scelidosaurus. This form of the hgemal canal or slit has every 

 appearance of being natural, and not due to any posthumous compression. The 

 hsemapophysial surface external to it is convex transversely, slightly concave 

 lengthwise ; the lamina3 slightly contract to their union in the spine, which becomes 

 compressed, and a little expanded from before backwards near its termination. 

 The articular surface, after the second haemal arch, is afforded in equal proportions 

 by the two conjoined centrums beneath their terminal junction. The transverse 

 process of the second caudal (ib., d) arises fi'om the anterior two thirds of the 

 vertebra, over the junction of the centrum with the neural arch ; a trace of the 

 suture indicating the pleurapophysial character of this process is discernible in this 

 and some following caudals. The length of the centrum is 2 inches 2 lines ; the 

 fore-and-aft breadth of the base of the transverse process is 1 inch 5 lines ; its 

 length is 2 inches 5 lines ; its terminal breadth is 10 lines, ending obtusely. The 

 transverse processes progressively decrease in all these dimensions in the following 

 vertebrte. The anterior zygapophyses (PI. 54, fig. 1, g) are twice the length of the 

 posterior ones {z'}, by which their extremities are overlapped. The fore-and-aft 

 breadth of the neurapophyses between these processes is 1 inch 2 lines ; that of 

 the summit of the neural spine is 1 inch 6 lines ; the height of the spine from the 

 base of the prezygapophysis is 3 inches 4 lines. These dimensions are taken from 

 the third caudal vertebra. The five consecutive and coarticulated anterior caudal 

 vertebrae in the present block of Lias give a collective longitudinal extent of 12 

 inches. The distal half of the right femur (PI. 54, fig. 2, 65), and parts of the 

 right tibia (ib., 66) and fibula (ib., 67), are cemented to the vertebrae by the matrix. 

 Figure 1 in this plate gives a side view, fig. 2 an oblique under view, of the first five 

 caudal vertebrae. 



The succeeding (eighth) block includes the five vertebrae (PL 55, fig. 1) next in 

 succession. In these the length of the centrum continues to be a little over 2 

 inches, but they gradually decrease in other diameters, and especially in the size of 

 their diverging parts. The neural spine, in the ninth, is reduced to 2 inches 5 



