The ornamental design for a seatarm, as shown and described.
FIG. 1 is a left front perspective view of a new seat arm showing my new design in a representative embodiment;
FIG. 2 is a left side elevational view shown in a representative embodiment;
FIG. 3 is a front elevational view shown in a representative embodiment;
FIG. 4 is a partial right front perspective view shown in a representative embodiment; and,
FIG. 5 is a left front perspective view shown in a representative embodiment.
The views of the seat arm not shown form no part of the claimed design. The broken lines shown in the drawings represent a variety of environments, environments of varying lengths, or portions thereof and form no part of the claimed design. The dotted lines on the top part of the seat arm represent continuous stitching. The base is shown broken-away to indicate indeterminate width.