The ornamental design for a transitionalimage for a portion of a displayscreen, as shown and described.
FIG. 1 is a front view of the first image of a transitional image for a portion of a display screen showing our new design; and,
FIG. 2 is a front view of the second image thereof.
The appearance of the image transitions sequentially between the images shown in FIGS. 1–2. The process or period in which one image transitions to another forms no part of the claimed design. The broken line showing of the display screen, text, numbers, and graphic element in all views is for illustrative purposes only and forms no part of the claimed design.