The Land Of The Lost (The Land Of The Lost) (1948) - Noveltoons Theatrical Cartoon Series

This is a delightful cartoon, based on the old childrens' radio show. Two children, Isabel and her brother Billy, are in a rowboat (I think it's a rowboat) and catch a talking fish named Red Lantern. He gives them magic seaweed that will allow them to breathe under water and guides them to the bottom of the ocean and the Land of the Lost, where everything lost on earth eventually finds its way. Here Billy sees his lost jackknife, who tries to become a member of the Knights of the Square Table. He is at first rejected by the other knives (knights), but he rescues a kidnapped princess and becomes a member. Billy and Isabel return to their boat, with Billy glad that his jackknife now is happy.

There were three of these cartoons. The second one, "Land of the Lost Jewels" is still cute, but suffers from using footage from this earlier cartoon .. so that the two children do not remember having met Red Lantern, their fish guide, two years earlier. Isabel, the little girl protagonist, is named for the writer of the series, Isabel Manning Hewson (I think that was her last name).