184 



LYELL'S ELEMENTS OF GEOLOGY. 



Fossil Cephalopoda of Extinct Genera. 



Fig. 153. 



Ostrea vesicularis (Gryphaa globosa, Sow.)' 

 also in Upper Green-sand. 



FOSSIL CEPHALOPODA OF EXTINCT GENERA. 



Cretaceous Period. 



Fig. 154. 



a. Turrilites costatus, Gault. 



b. Same, showing the indented border of the partition of the chambtra. 



Fig. 155. 





^.e Chalk and Upper Greenland. 



Pig. 166. 



Portion of Baculites Faujasii, 

 White Chalk and Upper Green -sand. 



Fig. 157. 



Portion of Baculites anceps, 

 White Chalk and Upper Green-sand. 



