From the Wikipedia page about the film:
La Coquille et le clergyman (English: The Seashell and the Clergyman) (1928) is considered by many to be the first surrealist film. It was directed by Germaine Dulac, from an original scenario by Antonin Artaud, and premiered in Paris on 9 February 1928. The film follows the erotic hallucinations of a priest lusting after the wife of a general.
Although accounts differ, it seems that Artaud disapproved of Dulac's treatment of his scenario, and the film was overshadowed by Un Chien Andalou (1929), written and directed by Luis Buñuel and Salvador Dalí. To this day, Un Chien Andalou is considered the first surrealist film, and its foundations in The Seashell and Clergyman have been all but overlooked. However, the iconic techniques associated with surrealist cinema are all borrowed from this early film. In Lee Jamieson's own analysis of the film, the surrealist treatment of the image is clear. He writes:
The Seashell and the Clergyman penetrates the skin of material reality and plunges the viewer into an unstable landscape where the image cannot be trusted. Remarkably, Artaud not only subverts the physical, surface image, but also its interconnection with other images. The result is a complex, multi-layered film, so semiotically unstable that images dissolve into one another both visually and ‘semantically’, truly investing in film’s ability to act upon the subconscious.
– Lee Jamieson, 'The Lost Prophet of Cinema: The Film Theory of Antonin Artaud' in Senses of Cinema, Issue 44, July 2007
The British Board of Film Censors famously reported that the film was "Apparently meaningless" but "If there is a meaning, it is doubtless objectionable".
Artaud allegedly loathed the resulting film, shouting back at the screen during the premiere and calling director Dulac "a cow".