INDEX 497 



PAGE 



Wolsey shale, Montana, fossils in 57, loi 



Woodworth, Prof. J. B., species named after 88 



zvoodworthi, see Acrothele. 

 wortheni, see Oboliis, 



Wynnia, classification of 142, 148 



evolution of pi. 11 (pp. 140-141 ) 



Wyoming, boundary of Cambrian land area in 168 



Yogo limestone, Montana, fossils in 80 



York, fossils from 310, 340, 341 



York, Pennsylvania, fossils from 89, 304 



York formation, fossils from ' 304 



yorkensis, see Acrothele. 



Yorkia, classification of 142, 146 



evolution of pi. 11 (pp. 140-141) 



nature of shell substance 150 



Youngs Creek, Montana, fossils on loi 



Zacanthoides, a descendant of the Mesonacid^e 254 



compared with Albertella 18, 19 



Zacanthoides idahoensis, new species 26, pi. 3, figs, i-ii 



associated fossils listed 30 



compared with Albertella helena 29 



Mesonacis vermontana 29 



Zacanthoides spinosus and Z. typicalis 29 



mentioned .*. 25 



stratigraphic position and association 197 



Zacanthoides levis, stratigraphic position and association 184 



Zacanthoides spinosus, compared with Zacanthoides idahoensis 29 



mentioned 17 



occurrence of 30 



stratigraphic position and association 209, 210, 211 



Zacanthoides typicalis, compared with Zacanthoides idahoensis 29 



mentioned 2,Z, 35. 38 



occurrence of 29 



stratigraphic position and association 183 



Zacanthoides sp. undt., stratigraphic position and association... .181, 182, 183, 



196, 198 



Zaphrentis, stratigraphic position and association 200 



zeno, see Eoorthis. 



