FAUNA OF THE OOLITES. 75; 
drawings, of Medusz, 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 (Arche- 
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 Archzopteryx, 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 Archzopteryx 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 
