Another ID challenge as a preview for tomorrow's post. I know at least one of my regular readers will be able to get this easily if she sees it, so from her (she knows who she is) I'm going to require a species-level identification or close to. Everyone else, see what you can do:
The figure is in ventral view and the specimen is 130 µm wide. Attribution to follow.
Update: Identity now available here. Figure from Steidinger & Williams (1970).
Metereca: Crossing the Divide
23 hours ago in Catalogue of Organisms