I remember this one being a paperback sci-fi anthology or magazine in my dad's collection. I think it may have been a "Best of" annual or otherwise related to a science fiction magazine.
As stated in the title, the cover had a bizarre, somewhat grotesque image on the cover. The head of a human woman, wearing either a space helmet or perhaps an underwater helmet. I think the metal part was dark brown, and there was a flat glass faceplate in front. The body attached to the head was tiny, and reminded me vaguely of a prawn, or similar creature. As best as I can remember, anyway. It really freaked me out at the time (I was four or five, IIRC). That much I am certain of!
I'm almost positive this one comes from the 1970s.
I know there's not much to go on here, but does this ring any bells with anyone?