138 years later: new data on Callistochiton (Allerychiton) pachylasmae (Monterosato, 1879) from its type locality: the Strait of Messina

The second documented record of Callistochiton (Allerychiton) pachylasmae in the Strait of Messina is reported, 138 years after the original description from this locality. Some morphological features of this species are described better and figured with SEM, and the variability of the head valve sculpture has been examined. Published and unpublished data on the habitat and distribution of this rarely recorded species are briefly discussed, and a further complete specimen (from the Agamennone collection) is also analyzed.