A Mongst the Carboniferous Crinoidea in this Museum an abnormal form of Platycrinus pileatus, Goldf., from the Carboniferous Limestone of Bolland was recently discovered by me whilst cataloguing the collection. This specimen has only four arms and the calyx has suffered a corresponding diminution in the number of its plates. The cup is conical, and when viewed from the base roughly quadrangular: it expands somewhat rapidly so that its greatest diameter is only slightly less than its height.