80 HADROSAURUS. 
twenty seven lines wide, and present no mark for the head of a rib. The latter, 
however, appears to have been situated higher, exterior to the upper back part of 
the position of the anterior articular processes, which are rather wider apart than 
those of the preceding vertebre. 
No lumbar vertebra or portions of a sacrum were discovered with the collection 
of Hadrosaurus remains under examination. 
Kighteen caudal vertebre, probably less than half of the original number, form 
part of the collection. In all of them the body is moderately biconcave; the con- 
cavities being of nearly equal depth. The borders of the articular surfaces are 
strongly everted, convex, and prolonged below into pairs of robust, sloping abut- 
ments for the articulation of chevron bones. The sides of the body are concave 
longitudinally, convex vertically, and are defined below by obtuse ridges, extending 
between the anterior and posterior chevron abutments. ‘The under surface of the 
body forms a concavity with a square outline whose angles are produced by the 
abutments just mentioned. The articular ends are hexahedral in outline. 
Three vertebra, of which two are represented in Figs. 9, 10, Plate XII, from the 
commencement of the caudal series, are remarkable for their diminution in length 
and great increase of breadth and depth, in comparison with the dorsal and cervical 
vertebre. Their body averages thirty-one lines in length, and in the three speci- 
mens ranges from five inches and a half to six in breadth by about five inches and 
a quarter in depth. They appear to have been provided with strong transverse 
processes, as the broken roots of these extend from about the middle of the body 
to the conjunction of the latter with the vertebral arch. The spinal foramen is 
transversely oval, about nine lines in depth and fourteen in width. The breadth of 
the abutments of the vertebral arch is about fifteen lines. 
The articular processes have subcircular flat facets, those in front being directed 
obliquely towards each other, those behind looking obliquely outward and down- 
ward. The anterior ones project a little in advance of the line of the front articular 
surface of the body; the posterior ones overhang the back articular surface. 
The ten succeeding specimens of caudal vertebrae, of which six are represented 
in Figs. 11-16, Plate XII, exhibit a gradual but slight increase in length until 
they almost equal in this respect the posterior dorsals above described, and they 
undergo a gradual diminution in depth ‘and width. The body of the eighth speci- 
men in the series under consideration is about equal in bulk to that of the posterior 
dorsals above described; those in advance are larger, those behind are smaller. 
The first (Fig. 11) of the ten specimens has its body thirty-three lines long, sixty- 
one broad, and fifty-four deep; the sixth specimen has the body thirty-six lines long, 
and fifty-one lings broad and deep; and the tenth (Fig. 16) has its body thirty-eight 
lines long, and forty-three lines broad and deep. 
In succession, the abutments of the chevron bones become more distinctly defined 
on each side by an intervening notch, which, however, at no time extends to their 
base. 
The spinal foramen undergoes a gradual diminution in capacity and assumes a 
more circular form. In the second specimen of the series it is nine lines deep ana 
twelve wide; in the tenth it is eight lines deep and wide. 
