A dead shell of Polygyra tridentata Say (fig. /), found under the 

 Palisades near Fort Lee, N. J., had formed the lip and denticles, and 

 afterwards had lost three-fourths of the body whorl. The shell was 

 then carried forward about 3 mm. and a new lip and denticles were 

 formed. Mr. F. H. Ames has shown me a similar specimen from 

 Wyoming Co., N. Y. 



The cause of this injury is a puzzle to me. If a mouse gnawed the 

 shell why did he not persevere and secure the dainty morsel? Was 

 he interrupted by a hawk or a snake? Did water find its way into 

 the shell in winter, freeze and burst the frail vessel? Or did a fall 

 from the rocks cause the fracture? 



I have found several specimens of Polygyra albolabris at the foot 

 of a ledge with fractured shells. In some instances ihe evidence of 

 a fall was conclusive. Beside the patient lay the fragment of a mush- 

 room on which the unfortunate mollusk had been feeding. The rest 

 of the fungus was clinging to its stem ten or twelve feet up the steep 

 bank. The break in this shell was exactly opposite the aperture. The 

 next morning the snail was crawling about with its head thrust 

 through the fracture. For four days the foot and head were not 

 entirely withdrawn into the shell. On the fifth morning the head was 1 

 thrust from the natural aperture, and in one week the large break was 

 closed by a rude patch of epidermis and shell. This shell is now in 

 my collection. 



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