Poseidon

This beautiful fountain is located on the great lawn, between the front of the Idle Hour Mansion and the Connetquot River. It is (just) visible in a postcard of the mansion in 1901 in its current location. Does anyone know if this fountain was installed prior to 1901, for the first mansion? Is it an ancient sculpture? If not, is there an artist attributed to it – perhaps an artist that worked on the second mansion?