Drip in shower -- can't get to shower valve cartridge

[slnm]

Hi,

I've got a Koehler shower fixture. There's a drip in the showerhead and I thought I'd try to replace the shower valve cartridge. The problem is I've unscrewed and pulled out the plate, unscrewed and removed the shower handle, and now I'm stuck. I'm attaching photos of the plate and of the stuff covering the valve cartridge in the hope the someone can identify the thing and/or give me a suggestion for how to get to the cartridge. I've tried pulling and turning the black thing in front of the white plastic with no luck.

Thanks in advance.

Sol

 

[Mr_David]

Water off and screws out just pull on it.
Should pull out
MIXER-CAP-FOR-OLDER-STYLE-CORALAIS-(BRASS-STEM)

 

[slnm]

That was it. Thank you!

 

[lindastacy3]

Water off and screws out just pull on it.
Should pull out
MIXER-CAP-FOR-OLDER-STYLE-CORALAIS-(BRASS-STEM)

It is very interesting i never thought that it was such easy.