﻿PLATE XXI. 



Pig. 



1. Trigonia (/ibbosa, Sow. (Variety.) Portland Oolite, Tisbury. (Page 84.) My 



cabinet. 



2. „ Damoniana, De Lor. Portland Oolite, Swindon. (Page 88.) My 



cabinet. 



3. „ „ Another example. Portland Limestone, Isle of Portland. 



My cabinet. 



4. „ „ Another specimen from the same formation and locality ; 



2 a,2 b, upper and anteal surfaces of the same specimen. 

 My cabinet. 



5. „ „ Variety with small costae and wide ante-carinal space. 



Portland Limestone, Isle of Portland. My cabinet. 



6. ,, excentrica, Sow. Young example. Blackdown Greensand. (Page 94.) 



Coll. Royal School of Mines. 



7. „ „ An example of fully developed growth. Blackdown Green- 



sand. Coll. British Museum. 



