To relieve the tolerance necessary for the holding groove of a base plate made by casting with a casting mold by providing an improved holding means formed as a part of the base plate made by casting with the casting mold.

This filter has a seam lid to provide the holding groove 64 for receiving an external gasket. The groove 64 is formed by fitting the peripheral surfaces of the seam lid to each other by a tab 53 fitted through a slit to the flange 54 to the base plate. The groove 64 has an external wall provided by an upright wall 52, a base part provided by a peripheral surface 47 and a groove internal wall 44b provided by a rim 44. The holding means is provided by plural horizontal ribs referred to as plural lugs 68 projecting horizontally outward from the upper part 44a of the rim 44. The lugs 68 are arranged at equal intervals around the upper part 44a of the rim 44. The lugs 68 are not extended to the flange 54 and are in turn retreated to the groove internal wall portion of the rim 44 shown by 44b.