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FOSSIL REPTILIA OF THE 



vertebra above described and figured. Two views of the centrum, of half the natural 

 size, are given in Plate XII, figs. 2 and 3. The capacity of the neural canal (fig. 2, «) is 

 worthy of note ; it is rather Mammalian than Saurian, and implies a great development 

 and vigour of the muscular system. 



§ 4. Lumbar Vertebra. — The last lumbar vertebra (PI. XIX, I) appears to be 

 confluent with the first sacral (ib., si). Its centrum is 3 inches in longitudinal extent ; 

 the side is slightly depressed below the base of the neural arch, from which extends 

 a lumbar rib (ib., I, pi) 9 inches in length; this is 1^ inches in breadth at three inches 

 distance from its free extremity. 



This lumbar rib, and also that of the antecedent lumbar vertebra, are straight and 

 extend transversely to the axis of the vertebral column. The distance in a straight line 

 from the haemal surface of the lumbar centrum to the end of the last lumbar rib is 

 1 foot 3 inches. 



§ 5. Sacral Vertebra. — These are five in number (ib., s \— s 5), coalesced 

 together, and seemingly with their pleurapophyses. The antero-posterior extent of the 

 five sacral centrums is 1 foot 4-i inches, each centrum averaging 3^ inches in length. 

 After the first they increase in breadth and decrease in the transverse convexity of the 

 haemal surface, the middle ones showing traces there of a shallow longitudinal haemal 

 channel with thick low convex borders. The interspace between the heads of the third 

 pair of sacral ribs (ib., pi. 3) is 7 inches, between the fifth pair it is 6 inches. 



Fractures of the mass of matrix enveloping the pelvis exposed the close cetiosaurian 

 texture of these vertebras and the shape, in some degree, of the neural canal in a portion of 

 the sacrum. One (fifth) sacral vertebra was thus divided lengthwise through the centrum, 

 neural arch, and spine, and yielded the following dimensions : — Vertical extent 1 foot 

 5 inches ; ib., length of neural spine, G inches ; antero-posterior diameter of do., 

 3 inches 6 lines. This spine for a great part of its length was not in contact with the ante- 

 cedent neural spine. The neural canal partially depresses the upper surface of the centrum 

 of each sacral vertebra, probably in relation to venous sinuses rather than to ganglionic 

 enlargements of the myelon. The vertical diameter of the neural canal where it dips 

 down into the centrum is 2 inches 3 lines ; in the ordinary course of the canal, it is 

 1 inch 2 lines : but, as the fracture affording this view was not exactly along the middle of 

 the vertebra, the canal might gain more depth at that part. 



The central part of the sacral centrum shows a rather coarser cancellous texture 

 than the rest, or than is seen in any part of the centrum of an anterior caudal vertebra 

 (PI. XII, fig. 1). 



What appears to be the first sacral rib (PI. XIX, pi. 1) is slightly dislocated haemad, 

 and probably, at the same time, bent forward obliquely from above downward and 

 backward in a greater degree than natural, the haemal end of the articular surface 



