io6 
EXTINCT MONSTERS. 
twelve feet ; perhaps the individual it represents was not fully 
grown, but, on account of the absence of most of the neck vertebrae, 
it is impossible to give the exact length. Both hind limbs are 
entire and well seen, but of the fore limbs the hands are wanting. 
The former were provided with four “functional” toes — that is, 
toes that were used, — and one “rudimentary” or unused one. 
There were two big spines, one placed on each shoulder, and a series 
of long plates arranged in lines along the back and side. Plate 
IX. shows an attempted restoration of this remarkable Dinosaur 
based upon the skeleton just described. It seems to have been 
organised for a terrestrial rather than an aquatic life, but to have 
been amphibious, frequenting the margins of rivers or lakes. 
Professor Owen considers that the carcase of this individual 
drifted down a river emptying itself in the old Liassic Sea, on 
the muddy bottom of which it would settle down when the skin 
had been so far decomposed as to permit the escape of gases 
due to decomposition. In that case the carcase would attract 
large carnivorous fishes and reptiles, such as swarmed in this old 
sea, so that portions of the skin and flesh would probably be 
torn away before the weight of the bones had completely buried 
it in mud. In this way, perhaps, the loss of much of the 
external armature and of the two fore feet may be accounted 
for. The hind limbs, being stronger, were better able to resist 
such attacks, and they are therefore preserved. Like many other 
specimens, this fossil has, in the course of ages, been subjected 
to enormous pressure from overlying strata, causing compression 
and dislocation or fracture. 
But there were in existence during the long Jurassic period, 
other and even stranger forms of armoured Dinosaurs. One of 
these, only imperfectly known at present, was the many-spined 
Polacanthus.^ This remarkable monster had the whole region of 
the loins and haunches protected by a continuous sheet of bony 
plate armour, rising into knobs and spines, after the fashion of the 
^ From Greek — polus^ many, and acantha^ spine. 
