Synopsis et Index Systematicus Specierum, et recentium, et fossilum 611 Description of plates 641 Plate 1. Balanus tintinnabulum 641 Plate 2. Genus Balanus 641 Plate 3. Genus Balanus 642 Plate 4. Genus Balanus 642 Plate 5. Genus Balanus 642 Plate 6. Genus Balanus 643 Plate 7. Genus Balanus 643 Plate 8. Genus Balanus 644 Plate 9. Sub-Genus Acasta 644 Plate 10. Genus Tetraclita 645 Plate 11. Genera Tetraclita and Elminius 645 Plate 12. Genera Elminius and Pyrgoma 646 Plate 13. Genera Pyrgoma and Creusia 646 Plate 14. Genera Creusia and Chelonobia 647 Plate 15. Genera Chelonobia and Coronula 648 Plate 16. Genus Coronula 649 Plate 17. Genera Platylepas, Tubicinella, and Xenobalanus 651 Plate 18. Genus Chthamalus 652 Plate 19. Genera Chthamalus, Chamæsipho, and Pachylasma 652 Plate 20. Genera Pachylasma, Octomeris, and Catophragmus 653 Plate 21. Genus Verruca 654 Plate 22. Alcippe lampas 655 Plate 23. Genera Alcippe and Cryptophialus 658 Plate 24. Genera Cryptophialus and Proteolepas 660 Plate 25. Genera Proteolepas and Balanus 662 Plate 26. Structure of the Mouth and Thorax 664 Plate 27. Nervous System and Senses 666 Plate 28. Cementing Apparatus 667 Plate 29. Cirri and Larvæ, first stages 669 Plate 30. Larvæ of Lepas: second and last stages of development 671 Errata 674 Index 675 Plates 685 LIST OF ILLUSTRATIONS Woodcuts on page 3* Figure 1. Shell 3* Figure 2. Compartments 3* Figure 3. Compartments 3* Figure 4. Compartments 3* Figure 5. Scutum (internal view of) 3* Figure 6. Tergum (external view) 3* Figure 7. Tergum (internal view) 3* Woodcuts on other pages Figure 1. Rostrum with two radii, serving in Chthamalinæ for rostro-lateral compartments 36 Figure 2. Always serving for lateral and carino-lateral compartments 36 Figure 3. Carina, serving in the Chthamalinæ, also, as a rostrum 36 Figure 4. Octomeris 39 Figure 5. Chthamalus 39 Figure 6. Chamæsipho 39 Figure 7. Balanus 39 Figure 8. Tetraclita 39 Figure 9. Basal edge of wall of compartment in Balanus tintinnabulum 43 Figure 10. Edge of the radius of Balanus tintinnabulum 46 Figure 11. Portion of edge of basis of Balanus tintinnabulum 50 Plates Plate 1. Balanus tintinnabulum 685 Plate 2. Balanus 686 Plate 3. Balanus 687 Plate 4. Balanus 688 Plate 5. Balanus 689 Plate 6. Balanus 690 Plate 7. Balanus 691 Plate 8. Balanus 692 Plate 9. Acasta 693 Plate 10. Tetraclita 694 Plate 11. Tetraclita: Elminius 695 Plate 12. Elminius: Pyrgoma 696 Plate 13. Pyrgoma: Creusia 697 Plate 14. Creusia: Chelonobia 698 Plate 15. Chelonobia: Coronula 699 Plate 16. Coronula 700 Plate 17. Platylepas: Tubicinella: Xenobalanus 701 Plate 18. Chthamalus 702 Plate 19. Chthamalus: Chamæsipho: Pachylasma 703 Plate 20. Pachylasma: Octomeris: Catophragmus 704 Plate 21. Verruca 705 Plate 22. Alcippe lampas 706 Plate 23. Alcippe: Cryptophialus 707 Plate 24. Cryptophialus: Proteolepas 708 Plate 25. Proteolepas: Balanus 709 Plate 26. Mouth: Thorax 710