Found a pair of these together under a stone in small forest stream. Curled up when found, but became active when caught. Less than 10mm long.
Found under wood debris near a sewage pond.
On rotten log in woodpile
Video of it swimming back to an Ulva: https://www.flickr.com/photos/30314434@N06/19791278951/in/datetaken/
This was a rather large Kaburakia excelsa (Giant Flatworm). I often find them here during the minus tides, usually living under rocks.
Pink! And pretty big, about 1.5" long. Reddish splotch on the back. ID as per Lamb & Hanby, p. 114. Video: https://www.flickr.com/photos/30314434@N06/19164787114/in/datetaken/
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes (from the Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning worm) are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals. Unlike other bilaterians, they have no body cavity, and no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening...