The ornamental design for a rearportion of an automobile, as shown and described.
FIG. 1 is a front perspective view of a portion of an automobile showing our new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a front elevation view thereof;
FIG. 5 is a rear elevation view thereof; and,
FIG. 6 is a top plan view thereof.
The portion of the automobile in light contrast is environment and forms no part of the claimed design. The bottom view of the rear portion of the automobile forms no part of the claimed design. Our design includes the mirror image of the embodiment depicted, but this second embodiment does not include the fuel door.