150 EXTINCT MONSTERS 
and formidable skulls possessed by some other forms to be 
described further on. But it is clear that no animal with such 
a long neck as this creature had could have borne the weight 
of a heavy skull. Short thick necks and heavy skulls always 
go together. Indeed, the weight of the long neck itself would 
have been serious had it not been for the fact that the vertebrae 
in this part of the skeleton, and as far as the region of the tail, 
have large cavities in the sides of the centra. This cavernous 
structure of the vertebre gradually decreases towards the tail. 
The cavities communicated with a series of internal cavities 
which give a kind of honeycombed structure to the whole 
vertebree. This arrangement affords a combination of strength 
and lightness in the massive supports required for the huge 
ribs, limbs, and muscles, such as could not have been provided 
by any other plan. (See Fig. 51.) 
The body of the Brontosaur was comparatively short, with a 
fairly large paunch (see restoration, Plate XIX.). The legs and 
feet were strong and massive, and the limb-bones solid, As 
if partly in order to balance the neck, we find a long and power- 
ful tail, in which the vertebre are nearly all solid. In most 
Dinosaurs the fore limbs are small compared to the hind limbs— 
e.g. Megalosaurus, Iguanodon, and Scelidosaurus,—but here we 
find them unusually large. In this case, then, it is hardly 
possible that the creature walked upon its hind legs, as many 
of the Dinosaurs did. There can be little doubt but that many 
other fierce and formidable Dinosaurs were living at the same 
time and in the same region with Brontosaurus, whose remains 
are found in the Jurassic rocks of Colorado (Atlantosaurus beds). 
How this apparently helpless and awkward animal escaped in 
the struggle for existence it is not easy to conjecture; but since 
there is reason to believe it was more or less at home in the 
