NO. 6 MIDDLE CAMBRIAN BRANCHIOPODA, ETC. 



PAGE 



Sidneyia Walcott, synonymy 205 



characterized 158 



classification of 155 



labrum, or hypostoma of 158 



representing Merostomata 155, 163 



mentioned 148 



Sidneyia inexpectans Walcott, synonymy and discussion of new specimens 



205, and text fig. 10, p. 206 



compared with Eurypteriis 206 



compared with Pterogotus bilobus 206 



highly organized merostome 165 



Sidneyidse Walcott 205 



classification of 155 



Silurian, Hymenocarina in 155 



mentioned 165 



Silurian seas, descendants of crustacean fauna in 153 



Slate, chemical analysis of. by Mr. George Steiger 150 



spinifera, see Malaria. 



spinosa, see Canadia. 



splcndens, see Marrella. 



Stalked eyes, Opahinia. Waptia, Yohoia, and Hyuieiiocaris 159 



Steiger, George, chemical analysis of slate by 150 



Stephen formation, British Columbia, Canada 148 



Strabops, representing Merostomata 155 



Stratigraphic distribution, earliest representatives of the five subclasses 



of Crustacea, table 156 



four subclasses of this paper 155 



Structural features, discussed 157 



stupenda, see Bohemilla. 



Summit Lake, trail from Burgess Pass to 152 



superlata, see Leanchoilia. 



symmetrica, see Mollisonia. 



Table, cephalic, thoracic, and abdominal segments 158 



stratigraphic distribution of five subclasses of Crustacea 156 



theoretical evolution of Cambrian Crustacea 164 



theoretical lines of descent of Cambrian Crustacea 161 



Telson as an abdominal segment 158 



tenuis, see Yohoia. 



Thamnocephalinje Packard, compared with Opabinidse 166 



Thamnoccphalus, leg of, compared with Opahinia 168 



Thamnocephalus plafyurus Packard, compared with Opahinia regalis. .165, 169 



Theoretical lines of descent of Cambrian Crustacea, table i6r 



Thoracic appendages, discussed 159 



Thoracic segments, discussed •. 159 



Tonto, basal sandstone of Cambrian series 198 



Tontoia, new genus, discussed 198 



classification of 154 



tentatively referred to Microdiscidae Coquin 195 



mentioned 155 



