[7.] Palpus of [Pollicipes mitella].

[8.] Palpus of [Alepas cornuta].

[9.] Maxilla of [Lepas anatifera].

[10.] Maxilla of [Lithotrya dorsalis], exhibiting the horny, rigid apodeme (a) buried in muscles, together with the two other principal bundles of muscles.

[11.] Maxilla of [Ibla Cumingii].

[12.] Maxilla of [Lithotrya rhodiopus].

[13.] Maxilla of [Pollicipes polymerus].

[14.] Maxilla of [Pollicipes mitella].

[15.] Maxilla of Pœcilasma eburnea.

[16.] Outer maxilla of [Conchoderma virgata]; (a), orifice of the olfactory cavity, the inner delicate chitine membrane of which is seen within, the specimen having been treated with caustic potash.