are seen
at the terminal point, and the two cement-ducts can be
traced into them.

TAB. X.

_Figures all greatly magnified._

Fig.

1. Mandibles of _Pollicipes mitella_: exhibiting the upper (_a_)
and lower (_b_) articulations, and the three principal
muscles; the short upper cut off muscle runs to its
attachment at the base of the palpus.

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. _Po