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. 1 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 

 1 From Greek polus, many, and acantha, spine. 



