My original tumblr post was here. This image was originally posted by UDHCMH with the following explanatory text:

Astonishing Stories, November 1941.

Not quite a science-fiction-woman-in-a-glass-tube cover but close.

Cover illustrates Wilfred Owen Morley’s “My Lady of the Emerald” in which a scientific expedition travels deep into the wilds of South America seeking traces of a super-civilization that predated Atlantis and Mu. They find an ancient beauty, imprisoned in a jewel, who bewitches them all.

The image comes to us via notpulpcovers.