Other Anatomy
Pallial Water
Walter C. Blinn also studied the water that is contained within the mantle
cavity of land snails and he particularly looked at Mesodon thyroidus
(Say) and Allogona profunda (Say). He found that when snails
retract into their shells they expel, what Blinn came to call, pallial water
through the pneumostome (Blinn, 1964).
The source of this pallial water is most likely from ingestion or osmotic
uptake, but it can also come from the entry of water into the pneumostome.
This water can also be replenished by body tissues (Blinn, 1964).
Now, however, rapid withdrawal into the snail’s shell is not very common in
nature. It may occur in the presence of the predator, but in most cases when
a snail withdraws into its shell, the process is very gradual. Also,
withdrawal and even epiphragm were only completed after most of the pallial
water had disappeared or diminished. Blinn did not observe any emission of
liquid from the snails so he concluded that the pallial water passed into
the tissues of the animal (Blinn, 1964).
This pallial water in the mantle cavity of the snail is considered to be a
water reservoir if the snail seems to be under any conditions in which water
is scarce. This water can be used to help keep the snail hydrated and help
with the production of mucus (Blinn, 1964).
Shell
The shell of Allogona profunda (Say) is described as
having a thin, smooth coating on both parietal and basal regions with
microprojections completely to partially covered (Emberton, 1996).