How can I use TTF fonts in Firefox under X/Qt?

I've copied them to /usr/local/fonts, ran fc-cache, fc-cache cached them. But when I run Firefox in X/Qt and go to the font config dialog, I don't see the fonts, they're not up for selection. All I see is stuff like adobe-courier, adobe-helvetica etc. which are the xfonts from X/Qt install.

How can I enable the TTF fonts?