The article examines a kind of fabric described as ‘θάλασσαι’ in The Book of the Prefect (Τὸ ἐπαρχικὸν βιβλίον). The meaning of this term by both editors and commentators of the document has not been satisfactorily explained so far. It appears highly probable, however, that ‘θάλασσαι’,
because of the ‘marine’ origin of the word, can be associated with a textile from byssos – the socalled
sea silk, made from fibres produced by a mollusc pinna nobilis. The presence of this fabric in numerous ancient sources is indicated, incl. works of Aristophanes, Cicero, Herodotus and Plutarch.
Diocletian’s Edict on Maximum Prices, where the price of ‘marine wool’ is at the very high level
is also investigated.