MANUAL OF NATURAL HISTORY. 565 



enabled to enjoy an arboreal life among primeval 

 forest trees. The head of these curious creatures 

 was prolonged into a muzzle, well furnished with 

 sharp teeth, and their neck was long and bird-like. 

 From the same strata are derived the fossil remains 

 of a gigantic carnivorous Lizard allied to the Moni- 

 tor, having powerful teeth with serrated edges, and 

 which inhabited the banks of the ancient rivers. 

 This colossal saurian (Megalosaurus) appears to 

 have reached the appalling length of thirty feet. 

 The genus Spondylosaurus, an extinct form allied 

 to Ichthyosaurus, is from the Oolite of Moscow ; 

 two species of Pliosaurus, a gigantic reptile of the 

 same family, are from the Oxford clay; the La- 

 certine Geosaurus of Cuvier is from Mannheim ; and 

 from the Oxford clay is derived Idiochelys, a Marsh- 

 Tortoise of the family Emydidce. There are, more- 

 over, several genera belonging to the family Croco- 

 dilidce found in different stages of the Oolite, such as 

 the ^fllodon, Mystriosaurus, Macrospondylus, Gna- 

 thosaurus, Rachceosaurus, Pleurosaurus, Steneo- 

 saurus, and Pelagosaurus ; the Pcecilopleuron, of 

 the same family, is from the great Oolite of Ger- 

 many. 



From the Oxford stage are derived fishes of the 

 Ray tribe belonging to the genera Asterodermus and 

 Euryarthra. From this formation, also, are pro- 

 cured fourteen extinct genera of Polypteridce, sau- 

 roid fishes with homocercal tails, of which the Po- 

 lypterus of the Nile and the Gambia is the living 

 representative ; lepidoid fishes with homocercal tails, 



