structural:reformatting, structural:expansion
Roman Lusitania and Gaul

In his Natural History 9.4.9–11, Pliny the Elder, remarked that a triton (merman) was seen off the coast of Olisipo (present-day Lisbon, Portugal), and it bore the physical appearance in accordance with common notion of the triton, according to a deputation from Lisbon who reported it to Emperor Tiberus. One nereid was sighted earlier on the same (Lisbon) coast. Pliny remarks that contrary to popular notion, the true nereids are not smooth-skinned in their human-like portions, but covered with scales all over the body. Their mournful songs at death have also been heard by the coastal inhabitants. Also, multiple nereids had washed up on the shore according to the legatus/governor of Gaul, who informed the late Emperor Augustus about it in a letter.

Sixteenth-century Swedish writer Olaus Magnus quotes the same passage from Pliny, and further notes that the nereid are said to utter "dismal moans (wailings) at the hour of her death ", thus observing a connection to the legend of sea-nymphs and the sister Fates whose clashing cymbals and flute tunes could be heard on shore. Olaus in a later passage states that the nereids (tr. "mermaids") are known to "sing plaintively", in general.

It has been conjectured that these carcasses of nereids washed up on shore were "presumably seals".