In the 1963 film 'Jason and the Argonauts' there is a scene where a Greek Sea God (Poseidon/ Triton?) holds back the Clashing Rocks so the Argo can have safe passage. What was the name of the actor who played the Sea God?

I'm not finding who played Triton:

Jason, leading an intrepid band of warriors that includes Hercules himself, encounters the seven-headed Hydra, the winged Harpies, the metallic 200-foot-tall Talos, the Merman Demigod Triton, and a band of sword-wielding skeletons.

In despair, Jason throws Phineas' gift into the water; a giant merman surfaces from the water and holds back the rocks long enough to let the Argo pass through.

https://en.wikipedia.org/wiki/Jason_and_the_Argonauts_%28film%29

http://www.amazon.com/Jason-Argonauts-Todd-Armstrong/product-reviews/6302182522

http://www.amazon.com/review/R1MNHBE1TVMHNK

The actor I'm after appears 5:30(ish) in this clip:

http://www.youtube.com/watch?v=vGhnx_9z-zo&feature=related

The actor who played Poseidon's son Triton is uncredited. In his biography, the film's director Ray Harryhausen could not remember the extra's name though they had searched months to find an actor to fill the role. The actor was cast because he had arms long enough to hold the rocks and have the model ship pass under his arm.

In the imdb.com message board, a reader claims that the stuntman Terry Richards told him that he had played Triton except for the sequence when the boat goes under his arms because his arms weren't long enough. Richards, a longtime stuntman famous as the sword-wielding Arab that Indiana Jones shoots, started his career in 1963 in England, where the scene was shot, so it's possible his account is accurate. Another forum claims that the actor Doug Robinson, who played Eupaemus (uncredited)in the film also played Triton. So perhaps the other actor with the long arms is Robinson, a fellow stuntman.

The link below shows a cast list with the ambiguity concerning Triton. A picture of Doug Robinson is included.
theseventhvoyage.com/jasoncast.htm webpage no longer exists

Bill Gudgeon as Triton (uncredited)
https://en.wikipedia.org/wiki/Jason_and_the_Argonauts_(1963_film)#Cast

A further link from Harryhausen detailing the filming of that scene:
http://www.guardian.co.uk/books/2003/dec/20/featuresreviews.guardianreview16

It's interesting to note that in the original myth, Athena is the one who holds the rocks and pushes the Argo through. Triton was chosen by the moviemakers instead for dramatic effect; that he's also human (for the most part) allowed the producers to save money over costly stop-motion effects.

The original Argonautica passage by Apollonius Rhodius:
"Then a vaulted billow rushed upon them, and the ship like
a cylinder ran on the furious wave plunging through the hollow sea. And the eddying current held her between the clashing rocks; and on each side they shook and thundered; and the ship's timbers were held fast.
Then Athena with her left hand thrust back one mighty rock and with her right pushed the ship through"