107 



EXPLANATION OF PLATES, AND INDEX. 



[The Plates are numbered as they were published in the ' Annals and 

 Magazine of Natural History.'] 



PI. VII. (all in flint except figs. 1, 2, 3, 9 and 12). 

 Fig. 1. Transverse section of Cephalites longitudinalis, pp. 17 & 73. 



- 2. Transverse section of C. alternans, pp. 17 & 75. 



3. Oblique section of C. bullatus, p. 76. 



4. Vertical section of Ventriculites, showing base of body lodged and 



ensheathed in the root : the upper part showing the fold of the 

 membrane, p. 16. 



5 & 6. Vertical and transverse sections of the same specimen showing 



body lodged and ensheathed in the roof, p. 19, & see p. 97, note. 



7. Root seen externally ensheathing body, p. 19. 



8. Intimate structure of the Ventriculidae highly magnified, showing 



square and octahedral structure, p. 21. 



- 9. Cast in chalk of this structure, p. 23. 



10. The octahedral structure very highly magnified, p. 22. 



11. The dermis or underskin, pp. 23 & 31. 



- 12. The epidermis or polyp-skin, pp. 23 & 31. This specimen is broken 



away at the upper part, showing traces of the structure below. 



13. The polyp-cells : vertical section highly magnified, pp. 36 & 37. 



14. The mode of addition of fibre, p. 21. 



PI. VIII. (all in chalk except fig. 7). 

 Figs. 4 & 5. Casts showing the places of processes, p. 32. 



6. Polyp-cells highly magnified, p. 36. 



- 7. Root-fibre encrusted with chalcedony, p. 25. 



1. Ventriculites simplex, p. 55. 



2 & 3. Ventriculites impressus, p. 56. 



N.B. For Ventriculites quincuncialis see PI. VII. fig. 7, & p. 58. 



PI. XIII. (all in chalk, except fig. 6, which is in flint). 

 Fig. 1. Ventriculites muricatus, p. 61. 



2. Ventriculites tessellatus, p. 62. 



3 & 4. Different sections of V. tessellatus, p. 62. 



5. Ventriculites cavatus, p. 63. 



6. Ventriculites striatus. p. 63. 



7. Ventriculites mammiltaris, p. 64. 



N.B. For Ventriculites latiplicatus see fig. D, p. 66. 



8. Ventriculites decurrens, p. 66. 



9. Variety tenuiplicatus, p. 66. 



10. Ventriculites radiatus, p. 69. 



11. Section of V. quincuncialis, p. 59. 



12. Section of V. muricatus, p. 61. 



13. Plaits of V. striatus, pp. 63, 65. 



14. Plaits of V. mammillaris, p. 65. 



15. Plaits of V. radiatus, p. 67. 



N.B. For Ventriculites bicomplicatus see fig. E, p. 70. 



PI. XIV. (all in chalk). 



Fig. \. Cephalites longitudinalis, p. 73. 

 2. Cephalites guttatus, p. 74. 



3. Cephalites paradoxus, p. 75. 



