(A) Regional map showing the southern part of the North Sea basin with bordering countries and labeled capital cities (yellow) and the Antwerp area (red). (B) Close-up of the Antwerp area with color-coding for the outcropping Paleogene and Neogene strata underneath the Quaternary top layer. The sections of the fortification walls around Antwerps used by Van Beneden (1877) as localities for the Neogene marine mammals (including seals) from the Antwerp area are indicated by dashed lines and numbered as in Van Beneden (1877), using Vanden Broeck (1878). The ‘third section’ of Van Beneden (1877) is the type locality for both Prophoca rousseaui and Leptophoca proxima. (C) Stratigraphic legend for the Paleogene and Neogene strata from the Antwerp Area. Abbreviations: NL, Netherlands; GER, Germany; LUX, Luxembourg; FRA, France; UK, United Kingdom; BEL, Belgium; Lux., Luxembourg City; Plio., Pliocene; Pal., Paleocene; Pia., Piacenzian; Zan., Zanclean; Mes., Messinian; Tor., Tortonian; Ser., Serravallian; Lan., Langhian; Bur., Burdigalian; Aq., Aquitanian; Chat., Chattian; Rup., Rupelian; Fm., Formation. Image based on data from Dienst Ondergrond Vlaanderen (DOV; dog.vlaanderen.be).