GEOLOGY. 



179 



Inferior Secondary Earth. 

 Variegated Freestone. 



Thus called on account of their gray or reddish colour, 

 sometimes mixed. They are mingled with pudding-stones 

 and schistous marl, presenting great variety of shade, which 

 has procured for them the name of rainbow marl. Some ve- 

 getable fossils are here found, but no animal. 



Alpine Calx or Lias. 



Tints uniformly gray or blackish ; a compact paste rarely 

 granulated, including much clay. Here are found many 

 fossil shells (the arcuated Grypheus, a kind of Oyster, flexed 

 in form of a bow) ; rock salt belongs to this formation, but more 

 especially to the variegated freestone and the rainbow marl. 



Jurassic or Oolitiiic Calx. 



This latter name has been given to them because they 

 appear to form small round granules like fish eggs. We 

 here find the following fossils. Icthyosaurus, the head of a 

 lizard, but prolonged into a tapering muzzle, armed with 

 pointed and conical teeth ; vertebral column organized as in 

 fish; pelvis small and weak; four limbs, of which the hume- 

 rus and femur are thick and short, and the other bones, which 

 are flattened and close together, compose, when enveloped 

 by the skin, fins analogous to those of the Cetacea, They 

 live in the sea and crawl with difficulty. Plesiosauriis, limbs 

 a little more elongated and more flexible than in the preced- 

 ing ; shoulder and pelvis more robust ; neck slender, as long 

 as the body, composed of thirty vertébrée and some more, and 

 terminated by a very small head. Megalosaurus, form like 

 that of the Monitor ; size so enormous that if we suppose the 

 the same proportions as in the Monitor, it must exceed seventy 

 feet in length. Pterodactylus, tail very short ; neck very 

 long ; head large ; excessive elongation of the second toe of 

 the fore-foot, which is more than twice as long as the body, 

 and probably served to sustain some membrane which aided 

 the animal in flying. The remains of two species are found, 

 one of which might have been about the size of a common 

 bat, the other of a thrush. 



