2. Mandibles of _Lithotrya dorsalis_, exhibiting four (_aa_) roughened, thin, ligamentous apodemes for the attachment of the muscles.
3. Mandibles of _Scalpellum Peronii_.
4. Mandibles of _Ibla Cumingii_.
5. Mandibles of _Lepas anatifera_.
6. Palpus of _Lepas anatifera_.
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 _Poecilasma 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.
17. Outer maxilla of _Pollicipes mitella,_ showing the two principal muscles, and the prominent, tubular, (_b_) olfactory orifices.
18. Caudal appendages, and basal segments of the sixth pair of cirri, of _Lepas anatifera_; (_a_), anus; (_b_), caudal appendages; (_c_), lower segment of pedicel of sixth cirrus; (_d_), upper segment of ditto; (_e_), basal segments of the two rami.
19. Caudal appendage (right-hand side) of _Pollicipes sertus_.
20. Caudal appendage (right-hand side) of _Scalpellum Peronii_.
21. Caudal appendage (right-hand side) of _Scalpellum vulgare_.
22. Caudal appendage (right-hand side) of _Pollicipes cornucopia_.
23. Caudal appendage (left-hand) _Lithotrya dorsalis_; (_a_), caudal appendage; (_c_), lower segment of pedicel of sixth cirrus; (_d_), upper segment of ditto; (_e_), segments of one of the rami.
24. Portion of caudal appendage of _Lithotrya dorsalis_, highly magnified.
25. _Pollicipes polymerus_; anterior ramus of the second cirrus.
26. _Lepas anatifera_; a segment of the sixth cirrus, showing the arrangement of the spines; (_a_), main anterior spines, of which there is a corresponding row on the opposite side; (_c_), dorsal tuft.
27. _Pollicipes polymerus_; a segment of the sixth cirrus, showing the arrangement of the spines; (_a_), main anterior spines, of which there is a corresponding row on the opposite side; (_b b_), calcareous shields on the dorsal surfaces, with tufts of fine spines near their upper edges.
28. _Alepas cornuta_; sixth cirrus of; (_a_) basal portion of one ramus, consisting of numerous segments; (_k_), the other and almost rudimentary ramus.
29. _Poecilasma fissa_; segments of the sixth cirrus, showing the arrangement of the spines; (_a_), anterior spines; (_c_), dorsal tufts.