Internal anatomy of the sipuncula Siphonosoma australe from Thua Thien Hue province (body length = 28.31 cm and introvert length = 10.9 cm). Schematic drawing of mouth (A), contractile vessel (B), coelomic cavity after dissection of the body wall (C), retractor muscles (D) and rectum (E). 

cv, contractile vessel/introvert; tt, tentacles; cvv, contractile vessel villi; k, kidneys; es, esophagus; drm, dorsal retractor muscles; rt, rectum; in, intestine; lm, longitudinal muscles; vn, ventral nerve cord; vrm, ventral retractor muscles.