U. S GEOLOGICAL SURVEY OF THE TERRITORIES. 



MURIDiE, PLATE IV. 



Figs. 42-45, Arvirola riparius <194!>). Figs. 46-49, A. riparins (4858). 



Figs. 50-53, A. towusendi (6802). Figs. 54-57. A. xanlhognailius (12118). 



