Very nice!

I think that's it. I don't see the embolus in the third shot though, which is making me a tiny bit suspicious.

Derek, any chance of a closer view of the palps? More or less the same angle as the spider's left palp in the third image would be great.

thanks!

Wow, this guy sure is interesting! Looking closer at the original (and new) images, I don't think he can be S. grossa. The palp structure just seems too different, regardless of angle.

Would you be willing to try a few more shots of him? This could help solve some S. grossa lookalike problems later (and also confuse us more ;)).

My next guess based on what we can see of the palp and the pattern is Asagena medialis (formerly in Steatoda). If you have time to try again, here's a quick diagram using the angles in your third shot of how to rotate (arrows in red) the palp (spider's left):
http://i.imgur.com/YQg1DIT.jpg
The shell-like part (cymbium, back part highlighted in blue) needs to be facing away from the camera.

Also, figs 34-36. (all the same thing, but spiders from different locations) on this page are roughly what to expect if this is A. medialis:
http://www.biodiversitylibrary.org/page/4246321#page/492/mode/1up

Thanks!

very intriguing beast!

Awesome! I think it's fairly safe to call him Asagena medialis. The lighter palp shot isn't quite at the right angle, but the other species with this type of palp have seem to have the embolus longer and wrapping around more of the other structures.

very neat beast, do these also pack a painful bite?

You're welcome! I don't know about the bite. I rather doubt it, although I guess there might be some mild, short-lasting discomfort since some Steatoda species can produce it.

I'll try to post some better pictures, such an interesting beast!