Cumacea is a small but important Order of Arthropods that contains approximately 50 Pacific Northwest species. The largest of which can attain 1.5 cm (0.6 in) in length. A cumacean has a large cephalothorax (head and thorax) body region that is covered by a carapace (shell) that extends in front of the head as well as a slender, flexible abdomen (tail) section.

These creatures live in and on various sediments where they feed by removing organic material from particles such as sand grains. Unless disturbed, these tiny creatures are almost impossible for the naturalist to find. The remarkable accompanying photograph is a “one in a billion” shot.