Det. J.T.Lapp 2012 via Platnick & Shadab 1974 for the traquillus and speciosus groups.

The key was pretty straightforward, taking me to Trachelas depressus, volutus, and mexicanus. T. depressus is not known to the states. I ruled it out because the ventral portion of the duct is not visible in depressus, but it is visible here. T. mexicanus and T. volutus are very similar. The strongest difference was given in a way that requires having specimens: volutus has a shorter, thinner embolus tip. Reading the text, I discovered that the volutus tip has two forms, a completely thin one, and a stubby squared-off one, in which the thin tip is missing. This specimen appears to have a tip in the exact shape required of volutus, except for the thickness; maybe this is a mated specimen and thin part has been lost. In any case, the shape of the duct is an exact fit for volutus and not for any others.