106 THE SNAIL 



V. The aperture of the pedal gland (p. 121) i» 

 immediately below the inferior lip, between 

 the head and the foot. 



Pass a seeker into the aperture, and backwards along th& 

 gland. 



B. After Eemoval of the Shell. 



Twist the animal out of the shell, taking care not to 

 damage the upper part of the body in so doing. The shell- 

 comes off readily if the snail has been put in spirit for a short 

 time after drowning. 



1. The sheU. 



a. The colour varies a good deal in different specimens. 



The ground colour is a yellowish brown, marked - 

 by darker longitudinal bands running round the 

 spiral, and by transverse bands corresponding to- 

 the lines of growth. 



b. The nucleus is the oldest part of the shell, at the top 



of the spiral, corresponding to the umbo of the 

 mussel-shell. 



c. The mouth is oval, and notched posteriorly by the 



penultimate turn of the shell. Its lip is smooth 

 and slightly everted. 



d. The lines of growth are transverse ridges parallel. 



to the mouth, and indicating successive positions- 

 of the mouth- during the growth of the shell. 



e. The umbilicus is an opening on the under surface 



of the shell leading into the hollow axis or 

 columella. It is sometimes closed. 



CUp away one half of the shell with bone-forceps, and 

 grind the cut edges flat on a file or stone. 



f. The columella is the axial portion of the shell 



round which it is coiled ; it is formed by the inner 

 wall of the several turns, each of which overlaps 

 rather more than half of the preceding one. 



g. The structure of the shell. The shell, like that of 



