228 SMITHSONIAN MISCEIvLANEOUS COLLECTIONS VOL. 53 



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ophircnsis descendens, see Acrotreta. 



Ordovician rocks, sections of : 173, 191, 204 



ornatus, see Bathyuriscus. 



Orr formation, House Range 171, 175-177, pi. 15, fig. i 



Orthoceras 189 



Orthotheca corrugata Matthew 210 



major Walcott 197, 210 



sp. undt 199 



Oryctocephaliis reynoldsi Reed 211 



zvalkeri Matthew 211 



sp. undt 199 



Owenella typa, new genus and new species 180 



Paget formation, Mount Bosworth 171, 205, pi. 19 



Paget and Bosworth formations, Mount Bosworth, break between 215 



palliseri, see Ptychoparia. 



panderi, see Acrothele. 



pannula, see Micromitra {Iphidella). 



pannula ophirensis, see Micromitra {Iphidella). 



parvus, see Obolus. 



(Paterina), see Micromitra (Paterina) . 



perf actus, see Obolus (Fordinia). 



perscus, see Conocephaliis. 



perugata, see Kutorgina. 



Philhedra columbiana (Walcott) 210 



Pioche formation. House Range 171, 184, pi. 17 



piochensis, see Ptychoparia. 



Platyceras bellianus Walcott 210 



romingeri Walcott 210 



sp. undt 181, 183, 199, 213 



prima, see Bornemannia. 



primceva, see Acrotreta. 



Productus, sp. undt 200 



productus, see Bathyuriscus. 



prolificus, see Diccllomus. 



Prospect Mountain formation, House Range 171, 184, pi. 17 



Prospect Mountain limestone, Eldorado limestone proposed for 184 



Prospect Mountain sandstone, old formation name retained 184 



Prospcctensis, see Micromitra {Paterina) . 



Protospongia {spicules) 194, 209 



Protypus fieldensis, new species 213 



new species 213, 215 



sp. undt 214 



Pterocephalus ? 204 



Ptychaspis 176 



Ptychoparia cordillera: (Rominger) 211 



kingi (Meek) 180, 181 



palliseri Walcott 211 



piochensis Walcott 183, 197 



subcoronata (Hall and Whitfield) 196 



sp. undt 17s, 176, 178, 179, 180, 181, 182, 183, 189, 192, 193, 194, 



195, 196, 197, 198, 199, 201, 204. 205, 208, 

 209, 210, 211, 212, 213, 214, 215. 



