More wierd phonemes

I've been inspired by all the talk of phonology on the lsit recently, and
I'm rebuilding Thagojian phonology quite extensively.

I don't intend to lose the obscenely large consonontal inventory (yay!),
but I'm moving some of my 'symmetries' and allophonies around to give the
lang a slightly different feel.  It looks like it'll merge with the (also
in-development) "WT5" and "WT6" phonologies eventually, and I'll hopefully
end up with a good range of usual and unusual sounds.

I've also decided that the two phonemic vowels are going to be
differentiated front-unrounded vs back-rounded instead of close-unrounded
vs open-rounded, with deep representations /e/ and /o/ replacing the
earlier /M/ and /Q/  (x-sampa as always...)

Anyway, my question is:

Is there a natlang precedent (and/or existing name?) for the 'hissing'
consonant (fricative?) produced by keeping the tongue in a lax / schwa-like
position, and producing either voiced or voiceless breath with the teeth
together and causing friction?

It sounds to me somewhere between /S/ and /f/ (or /Z/ and /v/), but is
obviously a totally different sound.

Any (more) ideas, anyone?



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Pb