LIASSIC DINOSAURS. 105 



that direction to fully 3 inches at the truncate extremity, and in breadth to 2 inches 

 2 Hues. Towards its end the process is excavated anteriorly, so that the rough 

 terminal surface (fig. 2, pi.) abutting upon the iliac bone is reniform. Fracture 

 of an angle at this surface in the left transverse process shows a medullary 

 cavity of 10 Hues in diameter by 6 lines in the section as exposed, surrounded by 

 a fine cancellous, almost compact, osseous texture, of from 2 lines to 4 Unes in 

 thickness. 



The transverse processes of the other sacral vertebrjB gradually become shorter, 

 with corresponding decrease of breadth at their origin, but with equal or greater 

 expansion of their termination, that of the last {pi, « 4) measuring 2 inches 7 hues 

 in fore-and-aft breadth ; the transverse processes thus touch each other, or nearly 

 so, at their ends, and offer a continuous longitudinal surface for the ligamentous 

 or fibro-cartilaginous attachments of the iliac bones (62) . The total length of the 

 articular " sacro-iliac " tract, so formed, is about 10 inches; a very slight lateral 

 twist or dislocation makes it rather longer on the left than on the right side ; this 

 appears to have been due to great pressure after imbedding, and is accompanied by 

 fracture or dislocation of the pleurapophysial part of the transverse process of the 

 last two sacral vertebrge. 



The spinous process, in each of the four sacrals, is about 2 inches high and 2 

 inches 3 lines in fore-and-aft extent ; they touch each other by their rough, flattened 

 summits ; these are narrow anteriorly, gradually expanding to a breadth of 8 lines 

 at their posterior third, with a thick, rounded termination ; the position of these 

 spines is over the interspaces of the origins of the transverse processes, through 

 the backward inchnation or extension of the neural arches. The articular processes 

 are faintly indicated at their base, the posterior processes overlapping the anterior 

 ones of the succeeding vertebra. The longitudinal extent of the truncated summits 

 of the four sacral spines is 9 inches. 



The hinder fractured surface of the block containing the sacrum exposes part 

 of the first caudal vertebra, the rest being associated with the four consecutive 

 caudals in the seventh block of Lias (PI. 54, figs. 1 and 2). 



The first caudal vertebra has been dislocated from the last sacral, and twisted 

 half round, so that its spine lies upon the sacral transverse process ; the fracture 

 has passed through the spine and part of the neural arch. The length of this spine 

 (PI. 54, fig. 1, ns) from the upper part of the neural canal is 3 inches 6 lines, the 

 transverse process (d) is 2 inches 3 lines in length, but its vertical thickness is 

 reduced to 5 fines at 2 inches from its termination. The neural canal is 6 lines in 

 breadth and 10 lines in depth. The bases of the neural arch seem to show that 

 the anchylosis with the centrum had not here been complete. 



The length of the first caudal centrum (PL 54, c l) is 2 inches, the depth or 

 vertical diameter of its articular end is 2 inches 5 lines ; the surface is moderately 

 14 



