24 
FOSSIL REPTILIA OF THE 
of the arch and centrum than in the PL dolicliodeirus (Tab. Ill, fig. 4) or in PL Bernardi 
(for example, Monograph, 1862, Tab. IV, fig. 1 1), and their articular surfaces are more 
horizontal, the anterior ones (Tab. X and XI fig. I, z) looking almost directly 
upward, the posterior ones (ib. ^') downward ; in this character the present species 
resembles the PL homcdospondyliis. The neural spine is of subrhomboid figure, its 
height hardly exceeding the fore-and-aft breadth ; the anterior border is convex, and 
rounded off into the upper one, with a scarcely marked angle ; the posterior one is 
slightly concave, the angle between it and the upper border is blunted ; the antero- 
posterior extent of the base of the spine is 1 inch 4 lines, the height of the spine is 
1 inch 6 lines. The parapophyses (Tab. X, figs. 1 and 3, Tab. XI, fig. 1, pZ) are not 
anchylosed to the centrum. Their head, or articular surface (ib. fig. 2 pi), forms the 
thickest part ; the bone decreases as it stands outward, especially in vertical diameter, 
becoming flattened or depressed ; it then bends backward, sending a short process 
forward, like the tubercle of the Crocodile’s cervical rib, but developed from the same 
plane as the head ; the backwardly contained body of the rib decreases in horizontal 
and increases in vertical breadth, presenting a broadly convex surface outwardly 
(Tab. X, fig. 3 pi). The length of the cervical pleurapophysis in the fifteenth cervical 
here described from the fore part of the head to the posterior point, is 2 inches ; from 
the end of the tubercle to the posterior point is 1 inch 8 lines. The increase in the 
succeeding vertebrae is most in the pleurapophyses, next in the neural spines, then in 
the breadth of the vertebra, and least in the length of the centrum; this, indeed, 
varies somewhat, but not so much as appears in the figure 2 of Tab. XI, in which 
the matrix is left upon part of the inferior surface in two of the vertebrae. 
Resuming the consecutive examination of the spinal column we find, in the 
twentieth vertebra (Tab. XII, 20), the costal surface rises nearer the neurapophyses (w^) ; 
the rib has attained a length of 2 inches 8 lines. In the twenty-first (ib. 21 ) the 
costal surface reaches the neurapophyses (?ip), which contributes a little to its upper 
part by a diapophysial projection. The vertical extent of this costal surface is 1 inch, 
the length of the pleurapophysis is nearly 3 inches. In the twenty-second vertebra 
half the costal surface is formed by the diapophysis. The length of the rib {d) is 
3 inches 9 lines ; the anterior process or tubercle becoming shortened. It is shorter 
in the next rib {pi), the body of which is longer; and on the rib of the twenty-fourth 
vertebra it has disappeared. In the twenty-fifth vertebra (ib. d 1) the diapophysis 
is prominent, and forms the entire costal surface. The ribs of this instructive series 
of six consecutive vertebrae have been dislocated from their articulations, apparently 
by the operation of the pressure which rotated the rest of the vertebrae from the 
vertical to the lateral position, but they retain their relative positions to each other, 
the end of one extending beyond and below the fore part of the next, and, in a greater 
degree, as the vertebrae approach the back. The sides of the neural spines of these 
vertebras are roughened by irregular or granulate ridges, directed toward their 
