Just a tiny bit closer this time. :-)
This is viewed from nearly the same orientation and position as the previous ventral images. The lower left corner is the proximal end of the fang, and just out of frame is where it starts getting darker and eventually connects to the basal segment of the chelicera. The lighter-colored central diagonal area is the venom duct.
I'm not sure what the serrations are used for. Foelix, referring to H.M. Peters, suggests they are apparently used for clipping silk threads.(1)
That's fine if you're rebuilding a large web, but I've only noticed web clipping in one jumping spider, a cleptoparasitic Pelegrina proterva
while stealing food from a sheet web spider.
NB: The venom duct actually has a streaked and "chiseled" appearance throughout its entire length. The apparent smoothness results from its increasing diameter, eventually putting it outside the focus range of this 27-image stack. What you are looking at is basically a tiny horizontal slice through the center.