OF PETRIFACTIONS. 223 



are in general most numerous in those places where the 

 rock occurs in basin-shaped strata. Many attempts have 

 been made to determine the genera and species of these 

 animals, but hitherto with little success. It would ap- 

 pear that the greater number are fresh-water species, and 

 a few marine species. But the most remarkable fossil 

 organic remain hitherto found in this limestone, is that of 

 an animal of the genus monitor, of the class amphibia, of 

 which Cuvier has given an interesting account in his 

 great work on Fossil Organic Remains. 



Petrifactions of vegetables rarely occur in this lime- 

 stone ; we sometimes meet with branches of plants ana- 

 logous to the lycopodiumj and more rarely fragments of 

 ferns, and of plants allied to the genus phalaris, 



Amongst these fresh-water productions, we meet with 

 various fossil remains of marine animals, such as gry- 

 phites, pentacrinites, trilobites, and corallophites. 



3. Zechstein. 



This rock, in some of its characters, resembles the al- 

 pine limestone, but does not contain so many petrifac- 

 tions. Ammonites occur in it ; and pentacrinites fasci- 

 culosus, and whole families of gryphites aculeatus. It 

 contains more rarely the gryphites rugosus, terebratulites 

 alatus, terebratulites lacunosus, and probably also the te- 

 rebratulites striatissimus, T. obliquus, and T. variabilis. 

 It affords nearly the same species of milleporites and 

 coralliolites as are found in the bituminous marl slate. 

 It is worthy of remark, that nearly all the petrifactions 

 found in this formation are much broken. 



4. Coal 



Beds of coal occur in the zechstein, and also, accordr 

 ing to some mineralogists, in the alpine limestone, ac- 



