326 SECONDARY FORMATIONS. [Ch. XXIII. 



3. Oolite, or Jura limestone formation. 



This division, in which we do not include the lias, contains a 

 great number of subordinate members, several of which may 

 relate, perhaps, to periods as important as our subdivisions of 

 the great tertiary epoch. The shells, even of the uppermost 

 part of the series, appear to differ entirely from the species 

 found in the division No. 1. 



4. The Lias. 



The shells of the argillaceous limestone, termed lias, and 

 other associated strata, differ considerably from those of the 

 preceding group, as do the greater number of species of ver- 

 tebrated animals. 



5. Strata intervening between the Lias and the Carboniferous 



group. 



The formations which are referrible to the interval which 

 separated the great coal formations from the division last men- 

 tioned, are very various, and some of them, like the new red 

 sandstone, contain few organic remains. One group, however, 

 belonging to this period, the Muschelkalk of the Germans, 

 which has no precise equivalent among the English strata, con- 

 tains many organic remains belonging to species perfectly 

 distinct from the fossils of the lias, and equally so from those 

 of the carboniferous era next to be mentioned. 



6. Carboniferous group, comprising the coal-measures, the 

 mountain limestone, the old red sandstone, the transition 

 limestone, the coarse slates and slaty sandstones called gray- 

 wacke by some writers, and other associated rocks. 



The mountain and transition limestones of the English geolo- 

 gists contain many of the same species of shells in common, 

 and we shall therefore refer them for the present to the same 



