When placed in magnesium chloride the snail may initially extend the foot far away from the shell. If it does, take advantage of the opportunity to see the shell retractor muscle which runs vertically from the foot to the shell on both sides of the animal. It can be seen through the integument on the sides of the visceral mass. This muscle is formed of the fused right and left columellar muscles. Together they make a horseshoe, open anteriorly, around the body.
Water approaches the body from the left side of the head .
Some of it passes posteriorly in the left pallial groove and some of it enters the left side of the dorsal mantle cavity. In the mantle cavity the stream of water passes over the ctenidium and between its filaments, over the openings of the kidneys and intestine, and then exits the right side. Here it enters the right pallial groove and is moved posteriorly along the right side of the animal. At the posterior end of the body the currents from the left and right pallial grooves join and move away from the animal. These currents are generated by the ciliated epithelium of the mantle and gill.