The decorations on the spandrels are different, but have a common base. They always feature a central motif flanked on either side by palmettes.
The first spandrel is composed of these palmettes segmented by ribbed and scalloped lobes. The next spandrel is spalled, but still features a rounded motif at its tip. The third is distinguished by the presence of a grainy fruit topped by a double axial palmette. Finally, the last spandrel features a feline head spitting out a cross and two palmettes.
This last spandrel can also be seen in other baptismal fonts, such as the one at Termonde.
Lexicon :
Spalled : scratched, dehorned, from a badly applied blow.