PROC. ACAD. NAT. SCI. PHILA. 1911. 



PLATE XIII. 



5 



9 



._ k. 



13 



17 



' A 



<; 



10 



14 



18 



3 



11 



12 



,. 16 



lo 



19 



21 



09 



25 



23 



27 



® 



28 



PILSBRY AND FERRISS: MOLLUSCA OF GRAND CANYON AND 



NORTHERN ARIZONA. 



