506 



IN^DEX. 



Page. 



Torry Puuk, lock of 281 



BOut lieaHt of [1201 490 



[123] 497 



[124] 498 



[131] 601 



[200] 474 



T«rtiary fossils 7, 20 



, Fort Union 31 



history, summary of 222 



of theOri'iit I'laiiiH 24,187 



, White River iiud (Jretaccous, separation of.. 18j 



, <:(>i)j;lomerato at base of 188 



of the Blaclt Hills 44 



oil lower Iia)>i(I Creek 35 



White River 241, 36, 186 



, unconformity at base of 35 



Theca gregaria 400 



Thetis cireularis 417 



Thiu sections, examination of 494 



Tlion^liinnierschiefer 476 



Thracia arcuata 461 



gracilis 420 



subgracilis 419 



Thunder stoi-ms 310 



Timber 321 



bui-uing of 322 



Titanite in honiblende-gneiss 479 



trachyte 491 



Topography of lJo.\ Elder and Elk Creeks 272 



Castle Creek 261,203 



Ficnch Creek district 220 



Rapid Creek 269 



Spearfish and Bear Butte Creeks 277 



Spring Creek distiict 238 



the Bear Lodge country 283 



Black Hills, 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 



biot ite in 490 



calcite in 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 



tridyniito in 491 



Trachytie pitchstouc 483 



Trapezium bellefourchensis 364 



Pajjc. 



Trapezium subequalis 365 



(l'a< liymya) trancata 36S 



Trias : See lU-d Beds. 



Tridymit<! in trachyte 401 



Ti'igouia conradi 4Q0 



TritiiuifuMus ? tenuilineatns 463 



Turbo nebrascensis 432 



1'urrilites nebniscensis 451 



Tunis eoutiirta 422 



Twin lanicUat ious of |)Iagio<^Iase 479 



Unccmfomiity at base of White River group 24, 27 



between slates and schists .62, 263 



of Carboniferous on Mesozoic 130 



Jura and Red Beds 149 



PotwlaiD and Archxau 81 



I^'(l Beds an I Carboniferous 149 



Unio uucalis 460 



T ' 1)1 i ft, age of the 214 



Val vata ? scabrida 461 



Vauikora ambigua 430 



Varieties of rhyolit4S 486 



Veins, ferruginous 53,59 



interlaminated 228 



quartz 53,59 



Veniella humilis 414 



Venilia humilis 414 



Venus ? cireularis 417 



Viviparus gilli 461 



Volcanic : See Igneous. 



Volsella (Modiola) fonnosa 361 



pertennis 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 



top of [178] 521 



Water-shed of the Black Hills 217 



Water supply 311 



Websteria cretacea 461 



White River conglomerate, composition of 290 



mica in (|uartzite 474 



Whitewood Creek [213] 523 



topography of 280 



Whiskey Creek 259 



Whit* Eiver group : See Tertiary. 



White River group from Cheyenne to Fort Laramie.. 24 



at Rawhide Butte 27 



on Old Woman Fork 30 



Whitfield, Prof. K P 3 



Whitney, Prof. J. D., Cited 86 



Wiucheil, Prof. N. H., cited 114,132 



exploration by 15 



Yoldia evansi 409 



subnasuta 462 



ventricosa 462 



Zeolite 514 



radiated . ; 515 



Zone structure of sanidin 609,511,512 



