68 EXTINCT MONSTERS. 
The remarkably small head is one of the most striking features 
of this Dinosaur, and presents a curious contrast to the large 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 vertebree in this part of the skeleton, and 
as far as the region of the tail, have large cavities in the sides of 
Fic. 10.—Neck vertebre of Brontosaurus. 
1. Front view. 2. Back view. 
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 vertebra. 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. ro.) 
The body of the Brontosaur was comparatively short, with a fairly 
large paunch (see restoration, Plate IV.). The legs and feet were 
