Pretty ladies in a chorus line dance energetically, their skirts raised high. Then they raise them even higher and you can see they are wearing underpants that reach down to their stockings.
American Mutoscope & Biograph (which later became known as American Biograph) issued two identically titled films in May of 1898. Given that the actual dancers at the Moulin Rouge in Montmartre danced the Can-Can, wearing no underwear, revealing their privates to titillate their rowdy audience, out for an expensive evening of slumming in the best and safest manner, we can conclude that one of these versions offered the dancers clad as the live dancers were. I did not see that version.
Given the lack of information to differentiate the two versions, I'll post this review on both sites.