Nereid
Nereid , noun
[Latin Nereis, -idis, Greek Nhrei:`s Nhrhi:`s, Nhrhi:`dos, a daughter of Nereus, a nymph of the sea, from Nhrey`s Nereus, an ancient sea god; akin to nhro`s wet, Sanskrit nāra water, compare Greek na`ein to flow.]
1.
(Class. Mythology) A sea nymph, one of the daughters of Nereus, who were attendants upon Neptune, and were represented as riding on sea horses, sometimes with the human form entire, and sometimes with the tail of a fish.
2.
(Zoology) Any species of Nereis. The word is sometimes used for similar annelids of other families.