1910.] NATURAL SCIENCES OF PHILADELPHIA. 121 



The smallest individual in the lot measures, length 11, diam. 3.4, 

 whorls 12^. It has superior and axial lamellae. 



In another lot from a colony not far from Station 1, in 20 shells 

 opened the proportions are : 



Three lamella?, superior, axial and basal 4 specimens, 20% 



Two lamellae, superior and axial 10 " 50% 



One lamella, the axial 6 " 30% 



Two other small lots were taken a mile or two southeast from 

 Station 1, the shells resembling the type lot, though perhaps there 

 may be a greater proportion of slender specimens among them. 



HIGH R/DGE 



MESA 



Fig. 25. — Principal collecting stations in Big Emigrant Canyon. 



