Elmo Lincoln - 1889-1952
also made an un-credited appearance in Tarzan's Magic Fountain -1949
which featured Evely Ankers 1918-1985
who was in 1942's Sherlock Holmes and the Voice of Terror
There you have it there you are.
It is also interesting to note that the actual person to first play Tarzan on the big screen, child actor Gordon Griffith, had a Seven Degrees connection to Peter Cushing.