Added one more image of the epigynum:

It was originally just intended for comparison with the older spider linked to above, but actually shows the features Kaston illustrates. Heavy-handed back lighting was the culprit in my first attempt.

"Mystery solved!

You have indeed found compelling evidence that your specimen is a Robertus. I thought the presence of Tm1 made it a linyphiid for sure, but it turns out Robertus have those too! The comb, the mastidion and the hair-like pseudo-spines correct that impression. A side view of the chelicera would confirm it further by showing no stridulating file.

So I thought: maybe it's Robertus species #2, which I have as a solitary specimen from the San Juan Islands. Nope, epigynum not a match, though it's similar in other ways.

Then I got out some of the common Robertus vigerens for further comparison of somatic features. Voila, on glancing at the epigynum it appears pretty plain that the central structure that dominates the appearance in preserved R. vigerens, is simply invisible in live material. Erase that, and your female looks just like vigerens!"

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Phew. That took some doing! I would never have guessed R. vigerens from Kaston's figures. A big thanks to Rod for figuring that out. New species for the guide too!

I'll be releasing this spider after I feed her tonight. With all the extra shots taken, she's probably at least a little disgruntled!

Moved from Spiders.

Starting to wonder about Robertus again. It looks like there are serrated bristles ventrally on tarsus IV, and other characteristics seem to be matching fairly well with Kaston's (1946) description of genus Ctenium (=Robertus). Not sure if the "spines" I saw are actually spines, or just regular long hairs. In any case, I don't think this is one of the species featured in the paper.

This set is getting kind of big. I'm uploading shots as I work with the spider and keys so that others can follow along. She's cooperative and doesn't seem too disturbed about the process.