The Calcaires à Baculites Fm (Upper Maastrichtian) at Picauville and Cauquigny (Manche) provided more than 70 specimens of a boring showing a hemispherical to irregular chamber, frequently with an horizontal, sometimes stratified, roof. Few thin and rectilinear pipes are connected with the chamber; most are vertical, upwards or downwards, less frequently horizontal or oblique. This trace fossil is described and named Unellichnus calciforans igen. nov., isp. nov. This boring was done after the precocious lithification of the sediment, a bryozoan-rich calcareous sand. The borer remains unidentified: it is seemingly not a sponge, the functional morphology of which appears incompatible with the structure of the trace fossil.