index 573 



PAGE 



Olenopsis cf . americanus Walcott, described 37 



figured, pi. 6, figs. 8, 8a, b 57 



cleora Walcott, described 74 



figured, pi. 13, figs. 3, 3a 114 



crito Walcott, described 75 



figured, pi. 11, figs. 6, 6a, b no 



leuka Walcott, described 77 



figured, pi. 13, fig. 4 114 



Opabinia, dorsal shield (footnote) 176 



Ophileta ho Walcott 472, 474 



Ordovician crustacean leg 154, 430 



figured, pi. 36, figs. 1, la, 2, 20-d 208 



Glenogle formation 463 



Sarbach formation 459 



Orthoceras, new species _. 458, 527 



attavus Brogger 527 



longus Walcott 472 



robsonensis Walcott 472, 473 



utahensis Walcott 474 



Oryctocephalus reynoldsi Reed, figured, pi. 58, fig. 4 259 



Ostracoda, relation to Trilobita 168 



Ottertail formation 461 



Ozarkian 467, 468, 469 



Lower 



Bibb formation 469 



Briarfield formation 469 



Chushina formation 458 



Goodwin formation 466 



in Alberta 470 



Ketono formation 469 



Mons formation 459 



Potosi formation 468 



Sarceen formation 471 



species 480 



Ozomia lucan, new species, Ozarkian, described 531 



figured, pi. 125, figs. 1-30 554 



Packard, R. S 123 



Pachychalina, compared 282 



lobata Ridley, compared 285 



? punctata, compared 286 



Palaeochorda setacea 224 



Palaeophycus, compared 264 



Palaeosaccus dawsoni Hinde. 312 



compared 310 



Palaeospongia prisca, Sardinian sponge 264 



Paradoxides, position 120 



