ILLUSTRATIONS
ix
| 50. | Brachiopoda (Lingulella and Mickwitzia) | 318 |
| 51. | " (Mickwitzia) | 320 |
| 52. | " (Mickwitzia and Obolella) | 322 |
| 53. | Trilobita (Callavia and Wanneria) | 324 |
| 54. | " (Holmia and Olenellus) | 326 |
| 55. | Fig. 1. Robson Peak District. (Panoramic view from Shio Point, looking down Moose River Valley) | 334-335 |
| Fig. 2. Robson Peak District. (Panoramic view of Tah Peak, Mahto Mountain, and Calumet Creek) | 334-335 | |
| 56. | Fig. 1. Robson Peak District. (Looking south across Calumet Creek and Flats) | 336-337 |
| Fig. 2. Robson Peak District. (Looking southwest from south slope of Mahto Mountain) | 336-337 | |
| 57. | Fig. 1. Robson Peak District. (View from south slope of Mahto Mountain) | 338-339 |
| Fig. 2. Robson Peak District. (View from southwest slope of Titkana Peak, looking south) | 338-339 | |
| 58. | Fig. 1. Robson Peak District. (Panoramic view of the Robson massif from the ridge south of Mumm Peak) | 340-341 |
| Fig. 2. Robson Peak District. (Panoramic view of the Robson massif and adjoining mountains) | 340-341 | |
| 59. | Figs. 1 and 2. Robson Peak District. (Panoramic view of Mural Glacier) | 342-343 |
| 60. | Dikelocephalus minnesotensis Owen | 392 |
| 61. | Dikelocephalinæ (Dikelocephalus and Saukia) | 394 |
| 62. | " (Dikelocephalus) | 396 |
| 63. | " (Dikelocephalus) | 398 |
| 64. | " (Dikelocephalus, Saukia, Calvinella, and Conokephalina) | 400 |
| 65. | Dikelocephalinæ (Saukia and Dikelocephalus) | 402 |
| 66. | " (Dikelocephalus and Saukia) | 404 |
| 67. | " (Saukia) | 406 |
| 68. | " (Conokephalina, Osceolia, and Calvinella) | 408 |
| 69. | " (Saukia) | 410 |
| 70. | " (Calvinella and Saukia) | 412 |
TEXT FIGURES
| Fig. | 1. | Theoretical profile of North American continent | 10 |
| 2. | Diagrammatic reconstruction of imagined primitive Pelmatozoic ancestor | 43 |
