OF CONCHOLOGY. 85 



10. Diagram of Pompholyx, a pulmonate gasteropod, with 



a neural flexure of the intestine. Original. 



11. Diagram of a Cephalopod, after Huxley. 



12. Explanation of the signs used in the diagrams pre- 



ceding, a, branchial apparatus ; b, mouth ; c, 

 heart ; d, ovary and oviduct ; e, sub-cesophageal 

 ganglion ; f, anus. 



Plate 11. 



Fig. 1. Neural valve of Trimerella Billingsi, from a mold 

 taken from the natural casts by means of gutta 

 percha. Slightly restored. 



2. Side view of both valves of T. Billingsi in juxtaposi- 



tion. Restored from the casts. 



3. Section of the same. 



4. Haemal valve of Trimerella acuminata, Bill., (Cana- 



dian) from a gutta percha mold, 



5. Side view of haemal valve of Trimerella acuminata, 



Bill., from a mold. Restored (Ohio). 



6. Trimerella minor. Slightly restored from a mold of 



a neural valve. 



7. Apophyses of Ismenia ? (Frenula) Jeffreysi, much 



enlarged, from behind. 



8. The same, from in front. 



9. Side view of the same. 



10. Ismenia ? Jeffreysi, two and a half times the natural 



size. 



11. Magasella Cfouldii, three times the natural size. 



Note. There is every reason for supposing that the restora- 

 tions of the Trimerella here figured are essentially correct, yet, 

 as in all restorations, it is possible that there may be some defi- 

 ciencies in the representation of the more minute details. 



The diagrams on the preceding plate are made as simple and 

 as diagrammatical as possible, being only intended to show the 

 relative position of the several parts represented by arbitrary 

 signs. 



