the phyllopod bed, as it contains a large, unique, and fine series of phyllopod remains. It has a thickness of 7 feet, 7 inches, and is capped by a layer of coarse, bluish, dirty-gray shale weathering to a yellowish ochre-brown on the edges, that averages 18 inches in thickness. The phyllopod bed may be subdivided as follows from the top downward:
| ft. | in. | ||
| 1. | Bluish-gray siliceous shale with partings of dirty gray-colored shale | 1 | 9 |
| 2. | Dirty-gray shale | 0 | 8 |
| 3. | Bluish-gray shale in compact layers 3 to 4 inches thick | 1 | 0 |
| 4. | Dirty-gray shale | 0 | 2 |
| 5. | Bluish-gray, tough, brittle shale | 0 | 2 |
| Great Eldonia ludwigi layer. | |||
| 6. | Compact layer of bluish-gray hard rock that splits more or less evenly | 0 | 8 |
| 7. | Alternating dirty and bluish-gray shale | 0 | 9 |
| Great Hymenocaris perfecta bed. | |||
| 8. | The same character as No. 6: Compact layer of bluish-gray hard rock that splits more or less evenly | 0 | 8 |
| 9. | Dirty-gray, earthy shale | 0 | 2 |
| 10. | The same character as No. 6: Compact layer of bluish-gray hard rock that splits more or less evenly | 1 | 4 |
| This is one of the most important fossil-bearing layers—sponges, annelids, holothurians, and crustaceans. | |||
| 11. | Dark, dirty-gray, earthy shale | 0 | 1.5 |
| 12. | Bluish-gray, tough, brittle shale | 0 | 1.5 |
| This is the great Marrella splendens layer. | 7 | 7 |
Below No. 12 the layers of shale are arenaceous, irregular, and not favorable for preserving fine fossils.
In making the collections of 1910 and 1911 over 150 cubic yards of rock were quarried and split up. Frequently, however, many square feet of surface of the shale would be opened without exposing a desirable specimen.
Layer No. 12 is of great interest. It was a slab of this carried down by a snow slide that Mrs. Walcott and I found in 1909 on the trail from Burgess Pass to Summit Lake. It contains Marrella splendens in great numbers, and of the annelids it has yielded the only specimens of Miskoia preciosa and Amiskwia sagittiformis, and most of those of Pikaia gracilens, Wiwaxia corrugata, and Canadia spinosa. Among the crustaceans the only specimens of Opabinia regalis, Molaria spinifera, Yohoia tenuis, Y. plena, Mollisonia gracilis, and M. ? rara were found in it, and Burgessia bella, Waptia
