and 8 a flange 22 extending downwardly from the rim 20 c is arranged to engage the exterior surface of the cap body flange and provide a substantially leak proof seal between the lid and cap body and also to releasably lock the assembly together as will be more fully explained in connection with fig1 u2013 13 the flange 22 is provided with an interior sealing surface 22 a which is joined to a lower rounded surface 22 b terminating at a free end 22 c the exterior surface 22 d of the flange 22 is spaced from the interior surface 20 d of the depending portion of the peripheral rim 20 c as is illustrated in fig1 the sealing surface 22 a of the lid flange is oriented at an angle of u03bb to the vertical in the unstressed condition of the flange i e when the lid is in the open position and positioned horizontally see fig1 a downwardly extending hinge plate 20 e is formed integrally with the lid peripheral rim and carries at it 39 s lower end a pair of outwardly projecting axle stubs 20 f during assembly of the lid and cap body the axle stubs are forced into the semicylindrical bores 16 f at the end of the slots 16 e in the cap body see fig1 the slots are formed with a width slightly less than the diameter of the axle stubs to retain the lid on the cap body the hinge plate includes protrusions 20 g adjacent the fixed end of the axle stubs which engage the exterior surface of the cap body lower section when the lid is rotated to an angle of about.