466 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



represent the young of Z. spinosus. 1 The head differs in details, but not 

 more so than between the young and adults of Z. typicalis? 



Formation and locality: Middle Cambrian, Flathead formation, Crow- 

 foot section, Gallatin Range, Yellowstone National Park. 



BATHYURISCUS Meek? 

 PI. LXIV, fig. 6. 



A single specimen of the pygidium is placed provisionally under this 

 genus. Its principal characters are well shown in the figure. It is 

 associated with Hyolithes primordialis, and is probably from the Middle 

 Cambrian horizon. The genus Dolichometopus Angelin might include this 

 form, but with the material at hand it is difficult to make any detailed 

 comparison of generic characters. 



Formation and locality : Middle Cambrian, Flathead formation, east of 

 Dead Indian Creek, Absaroka Range, Wyoming. 



1 Bull. U. S. Geol. Survey No. 30, p. 184, PI. XXV, fig. 6. = Loc. cit., PI. XXV, fig. 2, 2a. 



