Moved from Hemiquedius ferox.

Since yesterday (September 25, 2017) three species are recognized in the genus Hemiquedius. See (1)
H. ferox seems to be restricted to peninsular Florida.
The insects don't care of political boundaries and I take the identification based on political geographic areas rather as a kind of statistical identification. But Massachusetts is pretty far from Forida and taking into account the difference of the climate and the habitat (even if both Massachusetts and Florida are on the Atlantic coast) I think that H. ferox can be eliminated from possibilities.
So, the beetle, from picture above, must be one of the other two species: H. infinitus or H. castoris.
If I would be force to say which one I will say 'probably H. infinitus' based on the how the beetle was found. I assumed that the log under which the beetle was found is not associated with the nest material of North American beaver or muskrat. (But this not work 100%. I wish to say that if H.castoris is associated with such nest material this not means necessarily that it can not be found under a log in the woods.)
So H.infinitus it is just an hypothesis. Maybe if you can enlarge the picture you can see how elytra look. See fig.1 and the text on article mentioned above.

I just noticed, the species should be "FEROX" and not vernix. Sorry about that (vernix goes with Ana*quedius)

Adam

You didn't only get the genus, but you even got the species!

I checked some specimens in the collection and can now say this is
Hemiquedius vernix. The impunctate elytra, elongate antennae and overall iridescence helped me make my choice. Now we have all the northeastern Quediine genera accounted for.

Cheers,
Adam

The suspense is building to see what you're suspecting:-)

We can place this in Quediina for now, I need to check some specimens to make 100% sure of what I'm suspecting.

Adam

Moved from Quedius.

because elytra appear impunctate.

A Quedius or one of the closely related genera.