Is anyone familiar with the growth from this beam?
House was circa 1850, basement was damp.

Thanks in advance.

Slime mold stalks?

I googled slime mold stalks and found some very similar images. I think that you may be right!

Thank you.

Sampling and examination under a microscope is the only way to tell which mold type it is. Btw, slime mold is not a fungi.
Slime mold is not a plant or animal. It’s not a fungus, though it sometimes resembles one. Slime mold, in fact, is a soil-dwelling amoeba, a brainless, single-celled organism, often containing multiple nuclei. Just saying…

I know a few folks like that.