English: A, Triton variegatum, to show the proboscis or buccal introvert (e) in a state of eversion.

a, Siphonal notch of the shell occupied by the siphonal fold of the mantle-skirt (Siphonochlamyda).

b, Edge of the mantle-skirt resting on the shell.

c, Cephalic eye.

d, Cephalic tentacle.

e, Everted buccal introvert (proboscis).

f, Foot.

g, Operculum.

h, Penis.

i, Under surface of the mantle-skirt forming the roof of the sub-pallial chamber.

B, Sole of the foot of Pyrula tuba, to show a, the pore usually said to be “aquiferous” but probably the orifice of a gland; b, median line of foot.