Mactra stultorum - a freak specimen from the Adriatic
A teratological specimen of Mactra stultorum (Linnaeus, 1758) from Grado, Italy (29.7 mm) is illustrated here. The ventral part of the shell clearly shows irregular growth. Most eye-catching is a prolongation of one part of the right valve which exceeds the median plane, thus filling the gap on the contralateral side of the shell. The observed atypical growth might have been caused by mechanical irritations to the mantle.