Our feral cat has come a long way in the year since we got it.  
Civilized...almost... but still not quite right.

A couple of times recently it's done something new.

Probably new to me bc it's finally getting to the stage where people can touch
it without losing blood and/or acquiring new scar tissue.

The behavior is this:   I'm sitting in a chair watching TV and the animal
approaches me, jumps up on my lap, presents it's head tb petted/scratched.

Everything goes fine for awhile and then it settles down in my lap - but this
time with my hand resting on it's body.

Seems tb fine for awhile, then it opens it's mouth really wide and bites down on
the two layers of PolarTec sweaters that I'm wearing.   It's a rather slow
motion for this thing - more like chewing than biting - but it just stays
clamped on there, moving it's bite a little in a sort of gulping motion.

If I move my hand the right way, it'll make a half-hearted try for my arm or
wrist.

Is there anything to explain here?