Forgotten Villains: Who's Mr. Poseidon?

Who's This? Forgotten Villains Week now looks at the bald Vulcan on the team. Who is he?

The facts: Before his appearance in DC Comics Presents, Mr. Poseidon appeared in exactly one 16-page story, in Sea Devils #2.
How you could have heard of him: If it wasn't through DCP, it's unlikely how you would have. He's the Forgotten Villain that wasn't even included in the Resurrection Man flashback story!
Example story: Sea Devils #2 (Nov.-Dec. 1961) by Bob Haney and Russ Heath

So it's your usual day for Dane Dorrance and the Sea Devils, testing a device that magnetically stalls battleship engines, when another diver steals it right from under their nose plugs.

Before they can reach the thief, he jumps into a high-tech mini-sub and zooms away. Looking for it and coming up empty, the Devils go ashore on a hunch and find a water bottle with a suspiciously familiar craft floating in it in the window of Nautical Notions and Supplies, Mr. Poseidon, proprietor. Kind of a silly place to keep it if it's in any way connected to theft and industrial espionage.

The Sea Devils should really be paying attention to the creepy man with the pointed ears wearing a wetsuit and/or communist utilitarian overalls, because he pulls a lever and...

They shrink and shrink and shrink until Poseidon picks them up, makes some rant about meddling in the affairs of "Mr. Neptune" (???) and drops them in the bottle. Soon, the cork is out of sight, the water becomes an ocean (which is why these guys ALWAYS walk around with air tanks strapped to their backs), and they're harpooning microbes and getting tangled in vegetable plankton. And when Mr. P gives the bottle a good shake, it's like a meteor swarm in there.

Turns out this cruel move was a bad one, because it throws the Sea Devils against the cork where they also find the stolen device, hidden in the microscopic world. The heroes use depth charges to blow a tunnel through the cork and the bottle soon springs a leak. Fearing their escape, Poseidon throws the enlarger ray on them just enough to see and grab them, but as a Forgotten Villain in the making, there MUST be a scene where he's defeated by an inferior enemy.

Using his wits, Dane Dorrance throws the enlarger ray into action, just as Mr. Poseidon pulls a gun, so...

And it's off to jail. No, I DON'T know why Mr. P has those pointed ears or where he got his tech. He works for (presumably) the commies, and I guess the ears are just a manifestation of his evil nature. Maybe if he were from some underwater species, but that's never mentioned, and he does need an air-breathing apparatus to work underwater. Even more confounding is the story's final punch, which requires you to think bottled restaurants are common.

Wow. That's a long way to go to make a lame joke make sense.

Mr. Poseidon is so lame, they had to give him a little boost in his Forgotten Villains appearance. There, he wore rings that allowed him to change size (a natural evolution of his tech) and control the final member of the team, the robot Ultivac. They had to make him do SOMEthing.

Who else? Ultivac! It's going to be Jack Kirbyriffic!