Muscles, ossicles and internal structures of the foregut of Porcellana platycheles are described and figured. The function of the foregut is deduced from the distribution of food particle size within its chambers. The trough of the cardio-pyloric valve is considered to be the main site of digestion and the supra-ampullary valve to have an active role in the formation of the ventral cap of faecal pellets.
The structures and function of the foregut of Galathea squamifera are similar to those of P. platycheles. Certain differences found in the foregut of Upogebia deltaura may be related to the small size of food particles ingested and the absence of a ventral cap from faecal pellets may be due to the supra-ampullary valve having no action on surrounding particles.