The Life‐History of the Agrionid Dragonfly

SHELLs oF Patella vulgata L. The actual lengths of the shells are as follows -Ist Row.-7 mm., 89 mm., 10 mm., 11 mm., 13°5 mm., 15°4 mm., 17°2 mm.2nd Row.-20°8 mm., 23 mm.(sexually mature), 266 mm.(about 12 months old), 30 mm. (15 months).3rd Row.-33'3 mm., 38°5 mm.(over 2 years), 40°7 mm.4th Row.-44'1 mm.(over 3 years), 47°3 mm.(about 4 years), 51°2 mm.(about 5 years).5th Row.-53'5 mm., 61°2 mm.These two limpets are at least six years old, and may be more.