viii
ILLUSTRATIONS
| TO FACE PAGE | ||
| 29. | Cambrian Trilobites (Holmia) | 392 |
| 30. | "" (Wanneria) | 394 |
| 31. | "" (Wanneria) | 396 |
| 32. | "" (Pædeumias) | 398 |
| 33. | "" (Pædeumias) | 400 |
| 34. | "" (Pædeumias, Olenellus) | 402 |
| 35. | "" (Olenellus) | 404 |
| 36. | "" (Olenellus) | 406 |
| 37. | "" (Olenellus) | 408 |
| 38. | "" (Olenellus, Callavia, Wanneria) | 410 |
| 39. | "" (Olenellus) | 412 |
| 40. | "" (Olenellus, Olenelloides, Holmia, Peachella) | 414 |
| 41. | Cambrian Trilobites (Olenellus, Pædeumias, Callavia) | 416 |
| 42. | "" (Callavia) | 418 |
| 43. | Eyes of Limulus and Olenellus | 420 |
| 44. | Genera of Mesonacidæ, showing lines of descent | 422 |
| 45. | Fig. 1. 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. 1. 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 Cambrian strata | 140 |
| 2. | Tangential section of Billingsella plicatella, x 200 | 151 |
| 3. | Tangential section of Dalmanella subequata, x 35 | 151 |
| 4. | Tangential section of Kutorgina cingulata, x 200 | 151 |
| 5. | Tangential section of Obolus 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 |
