1. The majority of the striae are perfectly parallel. Yet, given the saddle shape of the modified portion of the shell, something as deformable and convex as a finger or thumb could not have left straight, parallel incisions. And, even if it were possible for any material that could feasibly be rubbed against the shell, it still would not produce a palimpsest of straight and parallel modifications. It is much more likely that the specimen was resting on or encased in a "medium" containing silt when it was forced to move through the gritty medium in a straight line, by trampling or some other force (i.e. in this case, based on the space between the hundreds of parallel striae the silt would have been less than about 10 microns in diameter).
2. Although the authors have gone to a great deal of trouble to document the minute modification on the shell's internal surface, they provide no such documentation to support their claim that the specimen had once been covered with ochre, but had suffered surface attrition due to some "gentle post-depositional abrasion," which removed the previously extensive ochre as it partially removed the surface material and left tiny pits containing hematite across the outside of the shell. However "gentle" their theoretical "abrasion" may have been, it would most certainly have left its signature. After all, even 'polish' is simply the end product of countless abrasions removing ever smaller and smaller fragments of the material being abraded, using ever finer and finer abraders. That the authors did not seek to determine what might have caused the surface attrition severely weakens an already weak presentation.
3. The authors provide no specifics as to the actor or agent responsible either for the striae or the "gentle post-depositional abrasion." Their conclusions amount to nothing more than speculation about the processes necessary to produce the striae and the land-locked hematite pits.
4. Taken together, I see no reason to give any credence to the claims made in this paper, save the taxonomic ascription and the original size of the object.
Thank you for the opportunity to comment.