LIST OF ILLUSTRATIONS IN THE TEXT. 



^IG. 





PAGE 



PIG. 







PAGE 



— 



Parkes-Lapworth Mici 



•oscope... ... 3 



37. 



Tetragraptus fruticosus 





62 



1. 



Didymograptus bifidus 



i 6 



38. 



— pendens 





63 



2. 



— — 



6 



39. 



— Postlethwaitii 





. 64 



3. 



Divergence of the sti 



pes of Didymo- 



40. 



— serra 





66 





grapti 



7 



41. 



- reclinatus ... 





67 



4. 



Didymograptus extens 



us 9 



42. 



Bigsbyi 





69 



5. 



- nitidus 



10 



43. 



Trochograptus diffusus 





74 



6. 



— uniformis ... 



12 



44. 



Dichograptus oetobrachiatus \ 



ar. Sedg 





7. 



— cf. uniformis 



... 13 





wickii... 





79 



8. 



— patulus 



... 14 



45. 



— separatus ... 





80 



9. 



— hirundo 



16 



46. 



Clonograptus tenellus . . . 





84 



10. 



— sparsus 



17 



47. 



— Callavei 





84 



11. 



— superstes ... 



20 



48. 



Temnograptus multiplex 





86 



12. 



— ■ euodus 



22 



49. 



Bryograptus Kjerulfi ... 





87 



13. 



— affinis 



23 



50. 









88 



14. 



- gracilis 



25 



51. 



— — var. cumbrensis 





89 



15. 



— acutidens ... 



... 25 



52. 



— divergens ... 





90 



16. 



— Nicliolsoni 



27 



53. 



Trichograptus f ragilis . . . 





91 



17. 



— — var. planus 



29 



54. 



Azygograptus Lapworthi 





. 93 



18. 



— serratulus ... 



30 



55. 



— Hicksii 





94 



19. 



— simulans ... 



31 



56. 



— suecicus 





96 



20. 



- cf. filiformis 



32 



57. 



- ccelebs 





. 97 



21. 



— v.-fractus ... 



34 



58. 



Pkyllograptus typus ... 





99 



22. 



- — var. volucer 



35 



59. 



— august if olius 





. 101 



23. 



— deflexus 



36 



60. 



— anna 





. 101 



24. 



— Murcliisoni 



38 



61. 



Leptograptus cf. flaccidus 





105 



25. 



— — var. geminus 



41 



62. 



— flaccidus ... 





. 106 



26. 



— bifidus 



42 



63. 



— — var. spinifer ... 





. 109 



27. 



— am plus 



44 



64. 



— — — macilentus... 





. 110 



28. 



— cf. indentus 



46 



65. 



macer 





. Ill 



29. 



— nanus 



47 



66. 



— — — arcuatus ... 





. 112 



30. 



— artus 



48 



61. 



— capillaris ... 





. 112 



31 



— stabilis 



49 



68. 



— validus 





. 113 



32. 



— fasciculatus 



51 



69. 



— — var. incisus 





. 114 



33. 



— gibberulus . . . 



53 



70. 



Leptograptus grandis ... 





. 115 



34. 



Tetragraptus quadribr 



achiatus ... 57 



71. 



— latus 





. 116 



35. 



— Headi 



59 



72. 



Pleurograptus linearis var. si] 



inplex .. 



121 



36. 



— Amii 



61 



73. 



Amphigraptus divergens 





. 122 



