566 



IjSTDEX. 



Terry Peak, rock of '-- 281 



southeast of [1201 - - - - 49C 



[123] 497 



[124] 498 



[131] 501 



[206] 474 



Tertiary fossils - 7, 26 



, Fort Union 31 



history, summary of 222 



ofthe Great Plains 24,187 



, "White River and Cretaceous, separation of. - 18.3 



, conglomerate at base of 188 



of the Black Hills 44 



on lower Rapid Creek 35 



White Paver 241, 36, 186 



, unconformity at base of 35 



Theca gregaria 460 



Thetis circularis 417 



Thin sections, examination of 494 



Thonglimmerschiefer 476 



Thracia arcuata 461 



gracilis 420 



subgracilis 419 



Thunder storms 310 



Timber 321 



burning of 322 



Titanite in hornblende-gneiss 479 



trachyte 491 



Topography of Box Elder and Elk Creeks 272 



Castle Creek 261,263 



French Creek district 226 



Rapid Creek , 269 



Spearfish and Bear Butte Creeks 277 



Spring Creek district 238 



the Bear Lodge country 283 



BlackHills, origin of 210 



granite 227 



schists 55 



Whitewood Creek 280 



Tourmaline 70 



Trachyte 196, 197, 199, 201, 203, 483 



[174] 518 



a source of gold 282, 289 



apatite in 491, 519 



augite 489 



biotite in 490 



calcitein.. 519 



character described 488 



date of eruption 281, 289 



groundmass of 491 



groups of 527 



hornblende in 490, 519 



manner of occurrence 281 



on Rapid Creek 268 



pebbles in White River conglomerate 220 



plagioclase in 490 



relations of, compared with those of granite . 28 



sanidin in 489 



silica, percentage of 488 



titanite in 491 



tridymite in 491 



Trachytic pitchstone 483 



Trapezium bellefourchensis 364 



Trapezium subequalis 365 



(Pachymya) truncata 365 



Trias: See Red Beds. 



Tridymite in trachyte 491 



Trigonia conradi 460 



Tritonifusus ? tennilineatus 463 



Turbo nebrascensis 432 



Turrilites nebrascensis 451 



Tunis contorta 422 



Twin laniellations of plagioclase 479 



Unconformity at base of White River group 24, 27 



between slates and schists 62, 263 



of Carboniferous on Mesozoic 130 



Jura and Red Beds 149 



Potsdam and Archaean 81 



Red Beds an I Carboniferous 149 



Unio nucalis 460 



Uplift, age of the -. 214 



Valvata ? scabrida 461 



Vanikora ambigua 430 



Varieties of rhyolite 486 



Veins, ferruginous 53, 59 



interlamiuated - 228 



quartz 53,59 



Veniella humilis 414 



Venilia humilis 414 



Venus ? circularis 417 



Viviparus gilli 461 



Volcanic : See Igneous. 



Volsella (Modiola) formosa 361 



pertenuis 362 



Warren, General G. K., exploration by 10 



"Warren Peaks 103, 129, 199, 209 



[171] 517 



[210] -- 475 



Gold Ledge [187] 522 



[192] 523 



north of [174] 518 



southwest of [173], [175] 518, 520 



structure of 283, 284 



[175] 520 



topof[178] 521 



Water-shed of the Black Hills 217 



Water supply 311 



Websteria cretacea 461 



White River conglomerate, composition of 290 



mica in quartzite 474 



Whitewood Creek [213] 523 



topography of - 280 



Whiskey Creek 259 



White River group : See Tertiary. 



White River group from Cheyenne to Fort Laramie.. 24 



at Rawhide Butte 27 



on Old Woman Fork 30 



Whitfield, Prof. R. P 3 



Whitney, Prof. J.D., cited 86 



Winche'll, Prof.N.H., cited 114,132 



exploration by ■ 15 



Voldia evansi 409 



subnasuta 462 



ventricosa 462 



Zeolite 514 



radiated 515 



Zone structure of sanidin 509, 511, 512 





