NO. 6 MIDDLE CAMBRIAN r.RANCHIOPODA, ETC. 



PAGE 



Nevadia in Lower Cambrian and later faunas 157 



Notostraca Caiman 175 



Branchiopoda under 163 



classification of 154 



foreshadowed by Burgess shale fauna 165 



obliqua, see Hymenocaris. 



Odaraia, new genus, discussed 187 



classification of 154 



(footnote) 154 



rami, segmentation, and cercopods 159 



Odaraia alata, new species 188, pi. 34, fig. 2 



stratigraphic position and association 153 



Odaray, mountain peak, British Columbia, Canada 188 



Oesia disjuncta, stratigraphic position and association 153 



Ogygopsis klotsi (Rominger), associated with Mollisonia symmetrica. .. . 197 



Opabin, a pass, British Columbia, Canada 167 



Opabinia, new genus, discussed 166-167 



classification of 154 



epipodite and protopodite of 159 



female of 159 



somites of 167 



probable ancestor of Polyartemidae and Apodidge 165 



swimming exopodites of 160 



typical branchiopod present 163 



Opabinia ? media, new species 170 



Opabinia regalis, new species 167, pi. 27, fig. 6, and pi. 28, fig. i 



compared with Branchipus vernalis Verrill 168 



compared with Emeraldella brocki 203 



compared with Thamnocephalus platyurus Packard 165, 169 



eye of, compared with Leanchoilia superlata 171 



female of 169 



stratigraphic position and association 152 



suggestive of annelidan ancestor 163 



Opabinidse, new family, described and discussed 166 



classification of 154 



optata, see Habelia. 



Ordovician, Hymenocarina in 155 



mentioned 165 



Ordovician forms 190 



Ostracoda, descent of 160-161 



foreshadowed by Burgess shale fauna 165 



oldest known representative of 157 



traces of 148 



mentioned 155 



Ostracods in Middle and Upper Cambrian i57 



Otfoia minor, stratigraphic position and association 153 



