[A/S] Plumbing Question

[James Hall <james53@xxxxxxxxxxxxx>]

Sorry to pepper all of you with so many posts, but while I am at it.... :)
As I have been checking out the '68 Caravel, I was looking at the dump valve
for the Black water tank & I noticed a plastic dome sticking down about
where the shower drain would be located. Its white plastic about 7-8" in
diameter and it sticks down about 4-6", aparrently it must have taken a good
hit from the road for it is duct taped together, Can anyone shed some light
as to what this is (maybe a cover for the shower trap?!?) is it a factory
OEM item or a later owner modification? Any and all ideas are welcome.
Thanks James Hall