On the precipitatiopn and ripening reaction of the precipitates from a lead nitrate and an oxalic acid dissolved in ethanol, a new crystalline phase was obtained, whose X-ray diffraction data have not previously been reported. The crystal system was determined to be monoclinic. The unit-cell parameters were refined to a =10.613(2)$AA$, b =7.947(2))$AA$, c =6.189(1)$AA$, and $eta$=104.48(2)$^{circ}$.