This is one of the early Tarzan movies, starring Johnny Weismuller and Mauren O'Sullivan. Jane's relatives come to Africa to look for her to tell her she has inherited a fortune if she returns to civilization.
In the lizard scene, Tarzan is leading Jane and others through a steaming swamp that is full of man-eating Iguanas. (That's right, those harmless and popular pet lizards.) One of the men falls into the swamp and we see several lizards running towards the water and diving in after him. Then we see the man's hands held up out of the water as they slowly disappear. By the look on Jane's face, we know that the iguanas have torn his flesh to shreds and feasted on his corpse, turning the water red with his blood. (Maybe you should think about getting a pet Bearded Dragon, instead of an Iguana.) The movie doesn't show any bloody carnage, of course, but that's the way I imagined it - a pack of pet store lizards, on the wrong continent, ditching their vegetarian diets, and dining on human flesh.
Jane almost falls into the swamp, also, and some iguanas come running up to grab her, but some guy saves her. I think that part was just to give us another look at Jane's bare thighs under her little jungle outfit. That was a very racy sight for 1936, unless you were watching chorus girls in a musical.
The nasty hunter who was hired to bring Jane home (he put Tarzan in a cage to ship him home as a sideshow freak) wades into the water to grab a big stick to fight Tarzan with, but he falls into some quicksand and becomes Iguana chow. The bad guy is dead, and the lizards are well-fed. I love happy endings.
We see several Green Iguanas, but there is also another type of Iguana used here.