Snail
Snails are herbivores, so they have a plant based diet. They generally eat diatoms found on rocks. The radula (structure used for feeding; AKA tongue) is adapted to the food it eats. The food then travels to the stomach, which consists of several muscular layers. It is mixed with digestion enzymes Then, the food compounds travel to the intestine and nutrients are transported into the blood stream. The remaining waste is then excreted through the rectum.
Squid
The patterns of the squid's stomach varies on what it eats. Food is absorbed by cells lining the digestive glands derived from the stomach, and then enter the blood. Waste and undigested materials are compressed, then excreted through the anus into the mantle cavity and are carried away from the animals in the water currents. Excretory functions are carried out by a pair of nephridia, tubular structures that collect fluids and exchange substances with body tissue. The nephridia clear into the mantle cavity.
Clam
Food compounds are taken in through a siphon to the gills where tiny cilia move water, while food particles is caught by mucus. The mucus, with the food particles, is then moved to the palps, which pushes it into the clam's mouth. The food then goes into the stomach and digestion occurs. Digestive glands release enzymes. Nutrients are absorbed in the intestine. Waste is then excreted through the rectum and anus.