what is meant with acera

[Herman Hillebrand]

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In the title of the film 'Acera ou le bal des sorcieres' by the french
 cineast Jean Painleve, I found the word Acera. I can deduct from 
the description of the film, that it is probably the marine snail
Crepidula fornicata, but this animal is called in french textbooks
'crepidule'. Can anybody suggest the proper latin name?
hermanh at bio.vu.nl