Acoelomorph flatworms (also referred to as acoelomate flatworms or acoels) were formerly placed in the phylum Platyhelminthes with the polyclads. However, recent DNA work has tended to place them in a separate group, the Acoelomorpha. Some sources also place them (along with Xenoturbellida) in the phylum Xenocoelomorpha. They are typically very small (usually less than 5 mm) and lack the complex intestinal cavities of polyclads. They may be mistaken for small shell-less opisthobranchs but lack the well defined foot and other characteristics of such species. Representative Hawaiian species:

un. acoel sp. #1 CP: top & bottom: Hekili Point, Maui April 9, 2007

Convolutriloba longifissura CP: Hekili Point, Maui Nov 22, 2006

un. acoel sp. #2 CP: Hekili Point, Maui April 9, 2007

For more information see:   Acoelomorpha on Wikipedia   Flatworms on the Sea Slug Forum   Marshall Islands Aceols by Scott & Jeanette Johnson