AN-D CLASSIFICATION OF THE FOSSIL REPTILIA. 
251 
probably as long' as in succeeding vertebrae, where the measurement from the pre- 
zygapophysis to the articular diapophysial facet is 2'5 centims., and the process 
projects freely for more than a centimetre. The surface of the neural ai’ch is flattened 
and inclined concavely. Anteriorly, at a height of 2'5 centims., tliere is a slight, 
horizontal, zygapophysial facet, which probably had Jio function in the skeleton. The 
posterior zygapophysis is strong, and is developed backward in the usual way. The 
front to back measurement over these facets is 2‘5 centims. 
The neural spine exp'inds above into a hatchet shape, which is defined by a small 
concave notch above the pre-zygapophysis, and a larger concavity above the post- 
zygapophysis. Its superior border is concave from front to back, and 3 centims. long. 
It is fractured posteriorly, but is seen to have been a thick wedge of bone terminating 
in a point. Anteriorly it forms a blunt convexity more than a centimetre in transverse 
measurement. It makes some approximation in form to the neural arch of the fourth 
cervical of Protorosaurus Speneri,^'' though it difiers in having the posterior process 
superior in position to the post-zygapophysis. From the base of the centrum to the 
summit of the neural spine is 4 centims., of which the neural arch measures 2'7 centims. 
In the three succeeding vertebrae the characters are modified. The centrum is 
slightly shorter. The base of the fifth centrum shows a longitudinal median ridge, 
which is less elevated on the sixth and absent on the seventh, which is convex from 
side to side. The parapopbysial tubercles are more anterior in position, being just 
behind the anterior articulation, but quite as low on the side of the centrum. The 
transverse measurement over them is 2 2 centims. Behind these eminences the 
centrum is concavely compressed. The pre-zygapophyses are strong, directed forward 
and upward, convex externally, with the facet dmected inward and forward. Behind 
its rounded anterior margin, which is about 1 centim. wide, the process contracts a 
little. A blunt rounded ridge, which is concave in length, connects the zygapophyses. 
The neural spines incline a little forward as they extend upward ; they are about 
1 centim. wide. 
The posterior face of the last centrum shows a conical excavation, like the vertebra 
of an osseous Fish. The articular face is 2'1 centims. high and about 2'5 centims. wide. 
The ribs remain in close contact with the vertebrae. Their articular ends fork, 
so that with the processes from the vertebra they each enclose a sub-rhomboid space. 
The forks are of equal length, and diverge like the forks of a Y, but the tubercular 
process is the wider and the more compressed. The ribs are sub-cylindrical, curved, 
and half a centimetre wide ; that attached to the fifth vertebra is preserved lor the 
length of three centrums. 
Dorsal VertehrcB. (Plate 16, fig. 1.) 
A small slab from South Africa in the British Museum shows on the right side 
evidence of seven dorsal vertebrae, and on the left side portions of seven dorsal ribs. 
* ‘ Pliil. Trans.’, Vol. 178, p. 208. 
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