Paris Top 30 Attractions - One-Two-Go Paris: The Quick Guide to Paris 2015 - page 51

The decorated keystone upstream is named “Nymphes de la Seine” (the Seine Nymphs)
bearing the arms of Paris
There are two different keystone compositions, one on each side along the bridge at the
center of the arch.
The upstream keystone is the one you can see in the picture above and depicts the
Nymphes de la Seine (the Seine Nymphs) bearing the arms of Paris. The golden ship in the
middle is part of the Parisian coat of arms and is placed there to symbolize the French side
of the Alliance.
The one downstream looks very similar but is called the “Nymphes de la Néva” (Nymphs
of the Neva) having a golden version of the Russian coat of arms to symbolize the Russian
side of the Alliance.