On the other side (north face) is a small inverted triangle, about 6 inches across at its widest part. It looks like the sides of the triangle were made by working holes into the rock.
This boulder has been marked with stone tools, for some unknown reason.
Here is a sketch, since it is hard to photograph details on a large, shaded boulder. The larger holes to the left correspond to two brighter stars. This constellation is portrayed nearly vertical, instead of horizontal, as on page 47 of Manitou. This may simply be the native understanding of the Pleiades.