Rhabdocoelida, an order of the group of worms known as the Turbellaria (q.v.) or Planarians, and including those members of this group which are small in size with generally a straight, unbranched intestine. The sub-class was originally founded on the latter character, but it is now found necessary to include one group with a lobed intestine in this division. It is divided into three 1 sub-orders: - (1) the Accela, including some primitive marine forms without any intestine; (2) the Rhabdocoela, including the typical members with a straight intestine; and (3) Alloicoela, with a lobed intestine. The second order is that of the Dendrocoelida.