FAUNA OF THE OOLITES. 75 



drawings, of Medusae, which show that even at that time 

 this class had reached the state in which it still exists. 



The terrestrial fauna of the Jurassic period is like- 

 wise enriched by new forms and groups. We find the 

 first true crocodiles, tortoises, and the most remarkable 

 variation of the Sauroid type, the winged lizard or 

 Pterodactyl. It is evident from their well-preserved 

 skeletons that the wing membrane was stretched, as in 

 the bat, between the posterior and anterior extremities. 

 Behind, it extended to the foot, while in front, it obtained 

 a corresponding addition by the elongation of the little 

 finger. A first and only bird has likewise been found 

 in the well-known resting-places of the Pterodactyls, in 

 the lithographic slates of Solnhofen in Bavaria (Arch^- 

 opterix lithographica). The most remarkable peculiarity 

 of this bird, recognizable by the most minute impression 

 of its feathers, is the long tail, bordered by two rows of 

 rigid feathers. The head is unfortunately crushed beyond 

 recognition. The inferior order of Mammals already 

 mentioned, the Marsupials, were also present, as is shown 

 by the enclosures of the middle Oolite of England and 

 the upper Oolite of the Purbeck strata. 



The ornithic animals of the chalk, are more remark- 

 able intermediate forms than the Archseopteryx, and 

 these by their hour-glass-shaped vertebrate bodies are 

 directly connected with the sea-lizards of the Jura, and 

 also possess teeth ; this may, however, be the case with 

 the Archseoptcryx also. We shall return later to these 

 creatures, which fill up a void hitherto painfully sensible. 

 During this new period the Ammonites were most abun- 

 dant, and then became extinct, after going through a 

 stage of degenerate forms which may be observed in the 



