630 PROF. H. G. SEELEY ON THE DINOSAURIA OF 
facets for the chevron bones, which is rather less than an inch, 
because the middle of the base is occupied by a deep groove, more 
than } inch wide, which is boat-shaped, tapering away between 
the chevron facets. These facets are convex from front to back, 
and each is slightly concave from side to side; they round into the 
articular ends of the centrum, and are markedly distinct from each 
other at the posterior end, where they are longest. The length of 
the base of the centrum, between the anterior and posterior pairs of 
facets, is 2 of an inch. Above the transverse process is a pair of 
short strong ridges, developed at the posterior end, which are 
horizontal and just above the base of the neural canal. The neural 
arch is small, narrow, and depressed; its posterior end was removed 
by fracture, but anteriorly it is less than 4 inch wide, and the 
extreme measurement, from its summit, as preserved, to the base 
ot the centrum is 1,8, ich. The articular faces of the centrum 
are subhexagonal, and somewhat deeply impressed in the centre, 
especially the anterior face, which is 1,2, inch high and 1,4 inch 
wide. While the posterior face is not quite so high, it is a little 
wider, and is less markedly hexagonal, owing to the influence of the 
transverse processes in developing an angle on the upper third of 
the side. 
The next vertebra preserved is from a much lower position in the 
tail; it has essentially the same type of character, and measures 
18, inch in length along the neural canal, but is so much smaller 
in vertical and transverse measurements, that the anterior face is 
barely an inch wide and almost 44 inch in greatest depth. The 
posterior face has the same depth, and may have been a little 
wider. The articular faces are moderately concave, subhexagonal, 
and prolonged downwards into articular facets for the chevron 
bones, which are larger behind than in front. They are divided by 
a deep narrow groove, which runs along the middle of the base. On 
the middle of each side is a blunt somewhat rounded ridge, which 
helps to give the centrum its hexagonal aspect by dividing the side 
into two subequal regions, two of which converge downwards, and 
the other two converge upwards. Below these ridges, and nearer 
to the basal ridges, are two other moderately developed longi- 
tudinal ridges; and above also, on a level with the neural canal, 
are two more short ridges, sufficiently elevated to give a channelled, 
pinched appearance to the base of the neural arch, since another ridge 
runs along that region on each side. The neural arch is small, 
and its pedicle, +4, inch long, is placed nearer to the anterior than to 
the posterior end, as in Acanthopholis horridus. The neural arch 
has a median ridge, which rises a little as it extends backwards ; 
the arch is fractured, both at the anterior and posterior ends, and 
the neural canal is small. The height from the middle of the base 
of the centrum to the middle of the neural arch is 14, inch. The 
next vertebra shows all these characters, except that the neural arch 
is broken away, and indicates that the channel for the spinal cord 
was slightly excavated in the centrum. ‘The lateral spaces between 
the ridges are also rather more concaye. The length of this cen- 
