PART II. CHAPTER XVIII. 



225 



Fossils of the Lias. 



white colour, and have been called white lias. In some parts 

 of France, near the V osges mountains, and in Luxembourg, M. 

 E. de Beaumont has shown that the lias containing Gryphcea 

 arcuata, Plagiostoma giganteum, and other characteristic 

 fossils, becomes arenaceous ; and around the Plartz, in West- 

 phaha and Bavaria, the inferior parts of the lias are sandy, and 

 sometimes afford a building stone called by the Germans qua- 

 dersandstein. 



The name of Gryphite limestone has sometimes been applied 

 to the lias, in consequence of the great number of shells which 

 it contains of a species of oyster, or Gryphcea (Fig. 221.). 

 Many cephalopoda, also, such as Ammonite, Belemnite, and 

 Nautilus (Fig. 222.), prove the marine origin of the formation. 



Fig. 221. Fig. 222.^ 



{O.arcuata, Lam.) JVautihis truncatus, Lias. 



The fossil fish resemble generically those of the oolite, belong- 

 ing all, according to M. Agassiz, to extinct genera, and differing 

 remarkably from the ichthyolites of the cretaceous period. 

 Among them is a species of Lepidotus (Z. gigas, Ag.) Fig. 

 202.), which is found in the lias of England, France, and Ger- 



a Fig. 223. 



Scales of Lepidotus gigas, Agas. 

 a. two of the scales detached. 



many.* This genus was before mentioned (p. 348.) as occur- 

 ing in the Wealden, and is supposed to have frequented both 



* Agassiz, Pois. Fos. vol. ii. tab. 28, 29, 



