INDEX 463 



PAGE 



Mesonacis Walcott 261 



Cole, in synonymy 261 



Moberg, in synonymy 261 



Peach and Home, in synonymy 261, 267 



Walcott, in synonymy 261 



Weller, in synonymy 262 



compared with Albertella iQ 



Elliptocephala 269 



Nevadia • • • 257 



Olenellus 304 



Pccdeumias 266, 304, 306 



]Vanneria 298 



delimitation of genus 246 



development of, shown in diagram 249 



development of thorax in 244 



line extinct in Lower Cambrian 249 



mentioned 233, 236, 245, 247, 248, 250, 263, 288, 295, 306 



species referred to the genus listed 232 



stage in development of thorax defined 244 



stratigraphic distribution tabulated 251 



see also Olenellus {Mesonacis^. 



Mesonacis mickwitzi (Schmidt) 262, pi. 26, fig. 4; text figs. 16 and 17 



Peach, in synonymy 262 



compared with Mesonacis vennontana 263 



generic relations of 263 



mentioned 247 



stratigraphic distribution tabulated 251 



Mesonacis torelli (Moberg) 264, pi. 26, figs. 5-18 



compared with Olenellus .? sp 342 



hypostoma of 244 



mentioned 247, 341 



stratigraphic distribution tabulated 251 



Mesonacis vennontana (Hall) 264, pi. 26 ; figs. 1-3 ; pi. 44, fig. 2 



Marr on posterior segments of 3^3 



Moberg, in synonymy 266 



Walcott, in synonymy 265 



compared with Mesonacis mickzvifsi 263 



Nevadia weeksi 260 



Olenellus ? gigas 324 



Olenellus thonipsoni 338 



PcEdeumias transitans 306, 308, 338 



Zacanthoides idahoensis 29 



geographic distribution of 253 



mentioned 247, 250, 256, 264, 269 



posterior portion of compared with telson of Olenellus thonipsoni. 



233, 266 



stratigraphic distribution tabulated 251 



Mesonacis (Olenellus) Peach, in synonymy 261, 268 



