viii ILLUSTRATIONS 



TO FACE PAGE 



29 



Cambrian Trilobites (Holmia) 392 



30. " " {Wanneria) 394 



31. " " {Wanneria) 396 



32. " " (Pcedeumias) 398 



33. " " (Pcedeumias) 400 



34. " " (Pcedeumias, Olenellus) 402 



35. " " ( Olenellus) 404 



36. " " (Olenellus) 406 



37. " " (Olenellus) 408 



38. " " (Olenellus, Callazna, Wanneria) 410 



39. " " (Olenellus) 412 



40. " " (Olenellus, Olenelloides, Holmia, 

 Peachella) 4i4 



41. Cambrian Trilobites (Olenellus, Pcedeumias, Callavia) . . . . 416 



42. " " (Callavia) 418 



43. Eyes of Limulus and Olenellus 420 



44. Genera of Mesonacidas, showing- lines of descent 422 



45. Fig. I. Panoramic view of Bow Valley from near Laggan, 



Alberta 424 



Fig. 2. Fort Mountain from the west side of Corral Creek, 

 Alberta 424 



46. Fig. I. Ridge southeast of Ptarmigan Lake, Alberta 425 



Fig. 2. Panoramic view from the south slope of Fort 



Mountain, Alberta 426 



47. Map of a portion of Bow Valley showing approximate area 



of pre-Cambrian strata 428 



FIGURES 



1. Diagram illustrating known distribution of families in Cam- 



brian strata 140 



2. Tangential section of Billingsella plicatella, x 200 151 



3. Tangential section of Dahnanella subequata, x 35 151 



4. Tangential section of Kutorgina cingiilata, x 200 151 



5. Tangential section of Oholus apollinis, x 200 151 



6. Vertical section of strata in House Range, Utah 174 



7. Vertical section of strata in Blacksmith Fork Canyon, Utah. 190 



8. Vertical section of strata in Mount Bosworth, British 



Columbia 206 



9. Vertical section of strata in Mount Bosworth, British 



Columbia 207 



