Any measurable or observable characteristic related to the shape, structure, color, or pattern of the neurons located at the interface of the molecular and internal granule layers of the cerebellar cortex; these inhibitory neurons provide the output of the cerebellar cortex through axons that project into the white matter, and extensive dendritic trees from the Purkinje cells extend upward in a single plane into the molecular layer where they synapse with parallel fibers of granule cells.