158 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
processes of the fifth vertebra (fig. 59. t.p}) are very rudimentary, being reduced to 
the condition of short, slender, spicular outgrowths. Like their predecessors they 
arise from the arch of their vertebra by thin obliquely set roots, and are widely 
separated both from the former and from the transverse processes of tlie sixth 
vertebra. The latter, with the ribs which they carry r.'), are more strongly 
developed than any that follow them, but are otherwise normal. 
Thick superficial ossifications invest the lateral and ventral surfaces of the complex 
and two succeeding vertebral centra, but the sides only of the seventh centrum 
(fig. 59, S.O.S.). Beneath the centra of the complex, and the fifth and sixth vertebrm, 
the ossifications meet and blend in the median line to form the walls of a complete 
aortic canal («.c.). Dorsally and laterally the ossifications do not extend on to the 
ventral surfaces of any of the transverse processes, but terminate in a sharp longitu- 
dinal ridge on each side which forms the inferior boundary of a groove for the 
posterior cardinal vein. Lateral ridge-like thickenings {l.i'.) are developed on the 
sides of the anterior extremity of the complex centrum, and apparently mark the 
anterior limit of the superficial ossifications ; these ridges coincide with the dorsal 
insertion of the median section of the transverse membrane, and also of a portion of 
the fibres forming the corresponding region of the anterior wall of the air-bladder. 
Radial nodules (r.n.) are rejoresented by two elongated, slender nodules of bone lying 
along the lateral surfaces of the complex centrum at the dorsal extremities of the 
oblique lateral ridges, but united to the centrum by fibrous tissue only. There are 
no ossified dorsal laminae. 
The rigid connection of the anterior section of the vertebral column and the skull 
is secured by a peculiar development of dermal plates. The dorsal extremities of the 
two anterior interspinous bones are expanded into broad dermal plates, which are 
exposed on the dorsal surface behind the supraoccipital spine (fig. 61, The 
more anterior of the two {i.s.') overlies the interval between the divergent spines of 
the third and fourth vertebrae, and articulates in front by a straight suture with the 
supraoccipital spine (s.o.'), and behind with the posterior plates by a concavo- 
convex suture, the two plates, with the greatly expanded spine of the supraoccipital, 
forming a strong bony armature for the dorsal region of the trunk behind the head. 
At each of the postero-lateral angles of the skull, and overlying the true epiotic 
element, there is a third dermal plate (ep.o.) wedged in between the ascending process 
of the post- temporal (pt.a.) and the pterotic (pt.o.) in front, and the supraoccipital 
and the two dermal interspinous bones behind and above, but having its outer margin 
free. From its posterior margin the dermal portion of the epiotic is prolonged back- 
wards and downwards as a slender process of bone, which coincides with the superior 
margin of the lateral cutaneous area of its side, and serves for the anterior insertion 
of part of the donso-lateral muscles of the body wall.^ 
* As in Glyptosternum, the post-temporal, exoccipital, and epiotic bones form the walls of a deep basin- 
shaped depression near each of the postero-latei'al angles of the ci’anium. 
