ILLUSTRATIONS 



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TWENHOFEL : 



Figure 



Paee 



1 — Impressions made by rain-drops 361 



2 — Rain-drop impressions made on wet sand 361 



3 — Impressions made by artificial bail. 362 



4 — Drip impressions in soft mud 364 



5 — Impressions made by stranded bubbles 365 



6 — Impressions made by floating bubbles 366 



7 — Impressions made by bubbles rising tbrough mud and 



bursting on tbe surface 36S 



Tarr : 



Figure 1 — Sketch of concretion in Pennsylvanian shale in Boone 



Couutj% Missouri 377 



" 2 — Sketch of concretion in Mowry shale near Belle Fourche, 



South Dakota 377 



Powers : 



Figure 1 — Geological map of the Solitario uplift, Presidio-Brewster 



counties, Texas 418 



" 2 — Cross-sections of the Solitario uplift 420 



" 3 — Panoramic views of the exterior of Solitario uplift 424 



Kemp and Billingsley : 



Figure 1 — Map of the Sweet Grass Hills, Montana 438 



2 — Structure sections ; 442 



3 — Geological map of West Butte 447 



4- — Geological map of Middle Butte 451 



5 — Geological map of East Butte 454 



6 — Types of dikes and sills 460 



7 — Map of the Great Plains region of Montana 464 



8-^Columuar sections in the Sweet Grass Hills, Montana .... 469 



9 — Belly River section 470 



10 — Milk River section 470 



11 — Great Falls-Cat Creek section 472 



12 — Musselshell River section 472 



13 — Yellowstone section 474 



14 — Big Horn section 477 



(12 plates; 60 figures.) 



