This appears to be another newly documented species to Hawaii and perhaps elsewhere.  After consultation with Cory Pittman and John Hoover, I am going with their conclusion that it is an unidentified Euryleptid species based on its similarity to this flatworm from Singapore.   I wrongly assumed it was a Thysanozoon or Acanthozoon as the closest white flatworm of this minute size (10-12 mm?)  I have seen is another unidentified species from a similar area in North Kihei, Maui.  Cory points out that the papillae are low, conical and spaced far apart and the elongated marginal tentacles suggest a Euryleptid. Always smart to agree with someone who knows far more than you do.   In January of 2022, I came across three more similar worms in the shallows rubble area of Olowalu, Maui.  They all looked to be a variation of the same species, but with fewer papillae and one had noticeable red spots on the tips of its marginal tentacles.  I’ve included a couple of images of that individual and have linked this to John Hoover’s Flatworm site.  Follow-up:  In February of 2022, I came across one more individual that looked very much like the first one I found — only this time it was even smaller (4 mm?) and had more pronounced markings. It has far more pinkish-red on its body, its margins and papillae are more defined and its elongated marginal tentacles (when examined closely) seem to continue the subtle lace-like pattern of the margins. Are there two species here or are these differences just a reflection of their age/size?