INDEX 471 



Opabinia — Continued. page 



female of 1 59 



somites of 167 



probable ancestor of Polyartemidse and Apodidne 165 



swimming exopodites of i6o 



typical branchiopod present 163 



? media Walcott, new species described 170 



regalis Walcott, new species described 167 



figured, pi. 27, fig. 6 314 



pi. 28, fig. I 216 



compared with Branchipus vcrnalis Verrill 168 



Emeraldella brocki . 203 



Thamnocephalus platyiirus Packard 165, 169 



eye of, compared with Leanchoilia superlata 171 



female of 169 



stratigraphic position and association 152 



suggestive of annelidan ancestor 163 



Opabinidse Walcott, new family. described 166 



classification of 154 



Ophileta, fossils suggestive of 229 



? sp., Cambrian facies questioned 255 



listed from Potsdam-Hoyt fauna 254 



(Raphistoma) primordialis A. Winchell, listed from locality 78.... 361 

 ophirensis, see Micromitra (Iphidella) pannula. 

 optata, see Habelia. 



Ordovician 23 



apparent association of Upper Cambrian with 253 



forms 190 



genus, Dikelocephalus cited as, in Europe 366 



Hymenocarina in 155 



mentioned 165 



Robson Peak disti'ict, section described 331 



illustrated, pi. 58, figs. 1,2 340 



stratigraphic section 341 



system, stratigraphic section, Robson Peak district 22>^ 



orientalis, see Huenella and Syntropfiia. 



" Origin of Fauna," Walcott cited on Lower Cambrian 2 



ornata, see Amiella and Conokephalina. 



ornatus, see Conocephalites. 



Orthis linnarssoni Kayser (= Eoorthis linnarssoni (Kayser)), former 



and present generic reference yi 



(Plectorthis) agreste Walcott (:= Eoorthis agreste (Walcott)), 



former and present generic reference 71 



{Plectorthis) doris Walcott {^Eoorthis doris (Walcott)), for- 

 mer and present generic reference 71 



{Plectorthis) kichouensis WaAcott {^= Eoorthis kichoucnsis (Wal- 

 cott)), former and present generic reference... 71 

 {Plectorthis) linnarssoni Walcott {^Eoorthis linnarssoni (Kay- 

 ser)), former and present generic reference.... 71 

 {Plectorthis) sp. undt., Walcott {^Eoorthis sp. undt. (Walcott)), 



former and present generic reference 71 



