Family Synaptidae contains sea cucumber species that are small to quite large (Synapta maculata (Synapta maculata) grows to 2m in length ), long and snake-like. They lack both respiratory trees and tube feet. They are reasonably active, propelling themselves with waves of peristaltic contractions and aided by the adhesive nature of their tegument. The adhesion derives from their anchor-like spicules which may protrude through the skin. While some species can be very variable in colour and size, many species bear a close resemblance to one another - identification must be checked on spicule form. Clark (1907) and Heding (1928) should be consulted for an overview of this family.