Noah'S Ark Shell

The shell of Arca noae grows to about 10 cm (4 in) in length. It is shortened at the anterior end and elongated posteriorly. It is irregularly striped in brown and white and has finely sculptured ribs running from the umbones to the margin. The hinge is long and straight and the shell is attached strongly to the substrate by byssal threads. There are pallial eyes on the edges of the mantle, especially at the posterior end.

Arca noae is found in the Mediterranean Sea. It was once common in the Adriatic, but in 1949/50 there was a sudden unexplained, catastrophic decline in numbers. Since then, populations have been creeping back upwards, and in 2002, densities of up to 13 individuals per square metre (11 square feet) were recorded. However, due to a lack of records, it is unclear whether the population had returned to its previous size.