OOLITIC ERA. 



135 



ing every condition of sea-shore, and leaving their remains 

 in every degree of beauty and perfection. Gryphcea, ger- 

 villia, avicula, lima, ostrea, and pecten ; trigonia, modiola, 

 plioladomya, cardium, astarte, and scores of other genera, 

 occur in numerous specific forms in the marine beds of the 

 lias and oolite ; while fresh-water mussels (unionidce) are 

 equally characteristic of the estuarine sediments of the 



oorAric CEPHA.LOPODS. 



1, Ammonites Jason. ; 2, A. communis ; 3, A. Bucklandi ; 4, Belemnitea Puzcsianus 

 5, 6, Belemnites ; 7. Belemnoteuthis. 



Wealden. The gasteropods, too, in many generic aspects, 

 crowd the sea-shores turbo, trochus, pleurotomaria, nerincea, 



