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Other Greek mythical figures

The sea-monsters Scylla and Charybdis, who lived near the sirens, were also female and had some fishlike attributes. Though Scylla's violence is contrasted with the sirens' seductive ways by certain classical writers, Scylla and Charybdis lived near the sirens' domain. In Etruscan art before the sixth century BC, Scylla was portrayed as a mermaid-like creature with two tails. This may be tied to images of two-tailed mermaids ranging from ancient times to modern depictions, and is sometimes attached to the later character of Melusine. A sporadic example of sirens as mermaids (tritonesses) in Early Greek art (third century BC), can be explained as the contamination of the siren myth with Scylla and Charybdis.

The female oceanids, nereids and naiads are mythical water nymphs or deities, although not depicted with fish tails. "Nereid" and "nymph" have also been applied to actual mermaid-like marine creatures purported to exist, from Pliny (cf. §Roman Lusitania and Gaul) and onwards. Jane Ellen Harrison (1882) has speculated that the mermaids or tritonesses of Greek and Roman mythology may have been brought from the Middle East, possibly transmitted by Phoenician mariners.

The Greek god Triton had two fish tails instead of legs, and later became pluralized as a group. The prophetic sea deity Glaucus was also depicted with a fish tail and sometimes with fins for arms.