(136 



Plate X. 

 Maesenia leptoconcha, B. 



FIG. 



1. The shell, from beneath. 1/1. 



2. End of the hook of a lateral plate. 200 x . 



Aplysia Gilchristi, B. 



3. The animal, when living, natural size and colours. 



SiGARETUS planulatds, Recluz. 



4. The head with tentacles. 



5. A gill leaf. 



C. Prom the structure of the gill leaf. 100 x . 



7. The penis. 



8. A piece of the mandible. .350 x . 



9. A piece of the rasp, a, median plate ; b, lateral plate ; c, outer plates. 



200 X. 



10. Median plates, from the upper side. 



11. The same, from the under side. 



12. The same, obliquely from above. 



13. The lateral plates. 



14. Outer plates, from the backside, a, interior ; b, exterior. 



15. Outer plates, from the side. 



(Figs. 10-15 by Cam. 350 x .) 



16. The rasp-sheath. 



