The well known Santonian conglomerates from the area north of the Ham Mountains contain holes due to leached dolomitie pebbles of Kimmeridgian age, in which well preserved casts of "worm"-burrows have been observed. In smaller pebbles -- caused by the lack of space -- they were burrowed in narrow windings resembling the Serpulid genus GlomeruIa. However, their mode of winding differs from that of these Serpulids: The convex arches made by the boring organism must be regarded as a behavioural response when approaching the surface of the pebbles. In the lops of the burrows often a "Spreite" is found, but it is also observed in the convex windings and even parallel to the straight cylindrical burrows. That is in contradiction to the conventional definition of the "Spreite". The burrows which may belong to the Polychaetes are described as Lapispecus cuniculus n.g.n, sp. Other rare burrows have been identified as Dodecaceria (?) .