There are 9 known species of tiny shrimp-like organisms in this class. Most species are 2-3 millimeters in length. They are found in the sediment on the ocean floor from the intertidal zone to depths of 5,000 ft. Like all crustaceans, they have a head, a thorax, and an abdomen. They have 8 segments on their throax with appendages, and 11 segments on their abdomen with no appendages. They have small eyes that are buried in their exoskeleton.