Plate II. 

 Fig. 1. F. vicLvuiii/s, general anatomy, Iv. valve and 

 mantle lobe and right ctenidinm removed. 



Fig. 2. Transverse section throngli rib of sliell (P. 

 opercidaris). x 26. 



Fig. 3. R. mantle lobe showing distribution of pallial 

 nerves and muscles. Nat. size. 



Plate III. 



Fig. 4. Transv. sect, of mantle edge and velum, x 20. 



Fig. 5. Epithelium with eosinophilous cells, from the 

 mantle. x .300. 



Fig. 6. Transv. section of periostracal groove, x .350. 



Fig. 7. Foot, showing pedal groove, &c. 



Fig. 8. Transverse section through foot, along A. B., 

 fig. T. X 20. 



Fig. 9. Section through byssal gland. x 130. 



Fig. 10. Mucous glands from foot (P. maximus). x 480. 



Plate IY. 



Fig. 11. P. mcuvimus, blood vessels of 1{. mantle lobe 

 injected with lard mixture. 



Fig. 12. Penal organ, slit open, to show ridges and 

 vessels on inner surface. Xatural size. 



Fig. 13. Heart, distended with air. x 2. 



Fig. 14. Arterial system injected (P. nuurinius). Pallial 

 arteries omitted. 



Fig. 15. Leucocytes, and " clump " or pseudo-plasmodia. 

 X TOO. 



