614 PROF, H. G. SEELEY ON THE DINOSAURIA OF 
dorsal region was in proportion to the increase of pressure conse- 
quent upon its having to support the number of vertebree above it. 
No single centrum is well preserved in this dorsal region of the 
body ; but the neuro-central suture is marked by transverse ridges, 
and the underside of the centrum in the earlier part of the series 
is characterized by an angular or squeezed condition of the visceral 
aspect. This pinched appearance becomes lost as the series is traced 
backward, and in place of the inferior keel a well-rounded visceral 
surface is developed. ‘The neural arch preserved is strong, but not 
high; the transverse processes are given out horizontally from it, 
and the ribs may have been articulated to them exclusively. The 
sacral region is represented by three vertebre, but of such forms as 
to suggest that there were probably five or six; and the tail, re- 
presented by twelve vertebrae, presents the unusual condition of the 
vertebree becoming elongated as they pass downward in the series. 
The chevron bones, as indicated by facets for them, were at first 
unusually large ; but where the centrum has developed the hexagonal 
outline, which it afterwards attains when more elongated, the 
chevron bones must have been small, since no definite facets for 
them can be seen on the slightly rubbed articular ends. It is 
mainly on the evidence which this specimen gives of a strong sacrum 
and a long tail, such as could have acted as a balance to the weight 
of the anterior part of the body, that I am disposed to affirm the 
erect or semierect position of this Trumpington Dinosaur. The mo- 
difications which the vertebral column in consequence presents are of 
a type met with in no other Dinosaurian genus from the Cambridge 
Greensand. There is no approximation towards any of the typical 
American Dinosaurs, and there may be some uncertainty as to its 
relative position in the Dinosaurian order ; but it is probably affiliated 
to the Iguanodont family. Yet the ridges which give the remark- 
able compressed hexagonal aspect throughout the vertebre of the 
tail are so far similar to the ridges on the short caudal vertebre of 
Acanthopholis, as to suggest that the difference of form may be 
mainly a functional development consequent upon the different ways 
in which the bodies of the animals were carried. 
Dorsal Vertebre.—tThe first three vertebre are from the early part 
of the dorsal region. The centrum of the earliest preserved is 
about 1,8 inch long. The anterior articular face is broken, and 
the posterior articular face is nearly flat, without a central depres- 
sion. It is 13 inch wide and 1,4, inch deep to the worn visceral 
keel. Its outline was subtriangular. The sides of the centrum 
are concave from back to front, moderately convex from above 
downward as usual, and terminate in a sharp keel on the visceral 
surface. The greatest width of the centrum in the middle just 
below the neuro-central suture is 1,2, inch. The attachment of the 
neural arch was wide, $2 inch, and is marked by somewhat irre- 
gular grooves subparallel to the articular ends. The second ver- 
tebra is of the same length, has the articular surfaces more or less 
incrusted with phosphatic matrix, and differs chiefly in haying 
the sides of the centrum more inflated, so that the articular ends 
aii 
