220 NATURAL HISTORY 



ammonites, belemnites, nautilites, lenticulites, chamites, 

 terebratulites, anomites, and patellites. 



2. Greywacke. 



This is a rock, including in a basis of quartzy clay 

 slate, variously shaped masses of clay slate, greywacke 

 slate, flinty slate, and sometimes also masses and grains 

 of felspar, and scales of mica. It very rarely contains 

 petrifactions. Hence in maay extensive tracts of coun- 

 try where it predominates, not a single fossil organic re- 

 main is to be seen. The animal petrifactions which 

 have been discovered in this rock are ammonites, and 

 madreporites, of the same species as those met with in 

 clay slate, and greywacke slate ; also solenites, mytu- 

 lites, tellinites, and large orthoceratites. The vegetable 

 petrifactions are alleged to be fruits, stems and leaves of 

 palm-like vegetables, and parts of reeds. 



3. Clay Slate. 



It rarely contains petrifactions ; and the only kinds 

 hitherto met with in it appear to be ammonites and tri- 

 lobites. 



V 



4. Greywacke Slate. 



This rock seldom contains petrifactions. Where it 

 borders on the clay slate, it contains the same kinds of 

 ammonites as occur in that rock, and in the vicinity of 

 greywacke and transition limestone, we observe in it 

 orthoceratites, corrallites, and fossil remains of reeds 

 and marine plants. The orthoceratites gracilis of,Blu- 

 menbach, the Molossus of Montfort, and also the coral- 

 liolites orthoceratoides, which are found in this rock r 

 seem to belong to those remarkable corals that form a 

 kind of connecting link between shells and corals. Par- 

 ticular beds of siliceous and ferruginous nature, subor- 



