Sowerby. (Genera of Shells, published at 50, Great Russell Street, Bloomsbury,) gives satisfactory reasons for re-uniting the whole of the preceding under the name SERPULA. 6. MAGILUS, which burrows in coral; outer lip reflected. Fig. 9 to 10. 7. LEPTOCONCHUS, outer lip reflected. Fig. 11. 8. STYLIFER, spiral, thin, globular, living in Starfish. Fig. 12, 13. The three last genera should certainly find some other place in the system. SESSILE CIRRIPEDES. Lam. (_Sessilis_, low, dwarfish.) An order of Cirripedes, consisting of those which are attached by the base of the shells, containing the genera Tubicinella, Balanus, Coronula, Acasta, Pyrgoma, Creusia. To which may be added some other genera enumerated in explanation of figures 14 to 33. The shells of the Sessile Cirripedes consist of two different sets of valves: 1st. The _parietal_ valves, or pieces arranged in a circle, side by side, around the body of the animal, (an arrangement designated _coronular_ by De Blainville.) 2nd. The _opercular_ valves, or pieces placed so as to enclose the aperture. Between those opercular valves the ciliæ protrude which characterize the class. Besides these two sets of valves, there is generally a shelly plate, serving as a sort of foundation to the rest. The Sessile Cirripedes may be thus arranged. 1. TUBICINELLA. Six parietal valves, tube-shaped, opercular valves perpendicular. Fig. 14. 2. CORONULA. Six parietal valves, opercular valves horizontal. Fig. 15, 16, 17, 18. These two genera fix themselves in the skin of the Whale. The latter has been divided into the genera Chelonobia, Cetopirus, Diadema, and Chthalamus. 3. PLATYLEPAS. Valves divided, each having a prominent internal plate. Fig. 19. 4. CLITIA. Parietal valves four, opercular valves two, valves dove-tailed into each other. Fig. 20. 5. ELMINEUS. Parietal valves four, opercular valves four. Fig. 22. 6. CONIA. Parietal valves four, thick and porous at the base. Fig. 21. 7. OCTOMERIS. Parietal valves eight. Fig. 24. 8. CATOPHRAGMUS. Parietal valves numerous, irregular. Fig. 23. 9. BALANUS. Parietal valves six; opercular valves four, placed against each other conically in pairs. This genus has been divided into Acasta, Conoplea, Chirona, and Balanus. Fig. 25, 26, 27. 10. CREUSIA. Parietal valves four, supported on the edge of a funnel-shaped cavity. Fig. 28. 11. PYRGOMA. Paries simple, supported on a cavity. This genus has been divided into the genera Nobia, Savignium, Pyrgoma, Adna, Megatrema, and Daracia. Fig. 29 to 33. SETIFEROUS. Hairy.