CHART VII. 1,000 LITTORINA LITTOREA. NAHANT, MASS. 



18-19 mm. 



16-17 mm. 



-15 mm. 



So 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 yS 99 100101102103104105106 



