Plate XL. 



Fig. la, Ih. Trigonia pocillif<n'inis. A full grown specimen. 



,,2. ,, „ A young specimen. 



,,3. ,, ,, Cast, somewhat distorted. 



,, 4. Trigonia Ivikucliiana. A full grown specimen, 



,, bab. ,, ,, A somewhat smaller specimen. 5h, 



seen from the posterior side, showing the indistinct separa- 

 tion of area and escutcheon. 



„ 6. Trigonia Kikuchian-a. Cast, accidentally depressed on the 

 back. 



,, 7. Trigonia rotundata. Ivight valve. 



„ Sal). ,, „ Left valve of a full grown specimen 



partly restored, h, seen from the posterior side. 



,, 9. Trisfonia rotundata. Cast. 



,, 10. Helicoceras sp. 



,, 10(/. ,, ,, Transverse section. 



