1 66 



THE CHAIN OF LIFE. 



" Monitors," than any other existing form. The forc-Iimb 

 represented in the figure foreshadows very closely the bones 

 of the human arm and hand. Besides this we find in the 

 Permian certain lizards {Theriodonts of Owen) which present 

 the remarkable and advanced ])eculiarity already predicted 

 by some Carboniferous Microsauria/ of having distinct canine 

 teeth, producing adivision into incisors, canines, 

 and molars, in the manner of the Carnivorous 

 ([uadrupeds, which they seem also to have 

 resembled in some other parts of their skele- 

 tons. It is not impossible that the foot- 

 prints in the Permian sandstones of Scotland, 

 which have been referred to tortoises, were 

 those of animals of this type. Cope has 

 recently described from the Permian of Texas 

 a number of reptiles which have the complex 

 dentition of the Theriodonts, and others which 

 simulate that of Herbivorous mammals, by the 

 possession of flat grinding teeth supposed to 

 be adapted to vegetable food.''' The teeth of 

 all these Permian reptiles were set in sockets, 

 also an advanced peculiarity. Thus already 

 in the Permian, before the final decadence 

 of the Carboniferous flora, and while the 

 Palaeozoic invertebrates still lingered in the 

 sea, the age of reptiles dawned, and gave 

 ])romise of its future greatness by the as- 

 sumption on the part of reptilian species of 

 structures now limited to the Mammalia. 

 But the great Mesozoic reptiles were not fully enthroned, till 

 the Permian, an unsettled and disturbed age, characterised by 

 great earth movements, had passed away, and until that period 

 of continental elevation, with local deserts and desiccation, and 

 much volcanic action, which we call the Trias, had also passed. 

 ^ llyleopelon. ^ Diadictes and Bolasaiiriis (Cojie). 



Y\r,. 141. — Arm of 

 Proterosauriis 

 Sfieneri. Re- 

 duced. Permian. 



