This fountain and its sculptures date back to 1905 when they were created by Charles E. Tefft in bronze and marble, as the main sculpture in front of the Library Building. map
It was cleaned and repatinated in 2005 on the 100-year anniversary of the fountain. Also as part of this restoration, the mermaid and merman sculptures, which had been missing for decades, were re-created by Glenn and Diane Hines based on historical photos and returned to the fountain to make the restoration complete.
The fountain depicts a sea nymph with two seahorses pulling a seashell chariot through the sea, while the startled mermaid and merman scramble to get out of the way.
References:
● https://www.nycgovparks.org/parks/bronx-park/monuments/155
● https://en.wikipedia.org/wiki/LuEsther_T._Mertz_Library
● The Mermaids of Earth coffee-table book: See page 138 in the book about this sculpture.