Definition of "hemidemisemiquaver"

But the young gentleman […] walked down the dark side of the street in peals of laughter, making, ever and anon, little breathless remarks to himself, which his colleague could not hear, but which seemed to have the effect of setting him off again into new hemi-demi-semiquavers and roars of laughter […]

1863, Sheridan Le Fanu, The House by the Churchyard