490 ME. P. GEDDES ON THE MECHANISM 



Fig. 14. Ventral aspect of buccal mass: /, lips; j, horny jaw; vpr, sheet of ventral 



protractor fibres. 

 Fig. 15. Ventral protractors removed : vis, ventral longitudinal muscles of infraradular 



sheet ; vtr, ventral transverse fibres ; v'ti'', inner \ entral transverse fibres. 

 Fig. 16. Eadula turned forward : infraradular sheet and its muscles shown. 

 Fig. 17. Infraradular sheet cut away ; irs, its cut edge ; ac, the slightly inrolled apex 



of anterior cartilages. 

 Fig. 18. Transverse muscles all cut away, leaving framework ; vir and v'tr', their cut 



edges. 

 Fig. 19. Cross section of framework towards apex, showing deep sulcus. 



PLATE LXXXl. 



Fig. 20. Left side of buccal mass in situ: f, foot; I, lips;_;', jaw; s, skin of head; 



vp, ventral protractor ; Ipr, lateral protractor ; g, gullet. 

 Fig. 21. Superficial muscles removed, showing left of framework. 

 Fig. 22. Deep dissection, lateral cartilage removed ; irs, cut edge of infraradular 



sheet. 

 Fig. 23. Left anterior and posterior cartilages removed, thus completing median 



longitudinal vertical section. 



Fifjs. 24 to 34. Buccal mass of Buccinum. (24-31, x 3 ; 32-34, X 6.) 



Fig. 24. Skin laid back, dorsal aspect ; /•, radula, seen through window cut in gullet, gr ; 



nig, small muscles which attach gullet to skin ; dtf, dorsal transverse fibres 



sheathing upper part of apparatus ; mrs, muscle of radular sheath ; dim, other 



dorsal longitudinal muscles. 

 Fig. 25. Gullet removed, showing cpr, circular protractor of lips, and Ipr, lateral 



protractors. 

 Fig. 26. Dorsal transverse fibres laid back, showing mode of attachment of radular and 



underlying sheet ; c, the cartilages, their edges thickened by muscles ; rs, 



radular sheath, whence pass slips of muscle to cartilages ; dim, the complex 



dorsal longitudinal muscles. 

 Fig. 27. Radular sheath and muscles, all cut save the deepest set, dM \ vis, ventral 



longitudinal muscles. 



PLATE LXXXII 



Fig. 28. Ventral aspect, showing lower attachment of radula ventrally: vis, ventral 

 longitudinal muscles ; vtj", ventral transverse fibres ; g, depression leading into 

 gullet. 



