The pallial sinus is an indentation or inward bending in the pallial line on the interior of a

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of marine and freshwater Mollusca, molluscs that have laterally compressed bodies enclosed by a shell consisting of two hing ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

shell's valves that corresponds to the position of the siphons in those types of clams which have siphons (i.e. siphonate). The position of the pallial sinus is often clearly visible as a shiny line on the inside of the

bivalve shell A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two hinged parts or ''valves''. Bivalves are very common in essentially all aquatic locales, includi ...

.''Bivalves'' by J.H. Leal, Bailey-Matthews Shell Museum, Florida, USA http://www.shellmuseum.org/BivalvesLeal.pdf

References

Mollusc anatomy {{bivalve-stub