ARDEIRHYNCHUS N-G (PALAEACANTHOCEPHALA, POLYMORPHIDA, POLYMORPHIDAE),WITH A REDESCRIPTION OF A-SPIRALIS (RUDOLPHI, 1809) N-COMB

Ardeirhynchus spiralis (Rudolphi, 1809) n. g., n. comb. (syns Echinorh ynchus spiralis, Prosthorhynchus spiralis and Plagiorhynchus spiralis) , a parasite of herons (Ciconiiformes: Ardeidae), is redescribed on th e basis of the holotype from Ixobrychus minutus and specimens from Ard eola ralloides (new host record) in Bulgaria. A. spiralis is a member of the family Polymorphidae and not of the Plagiorhynchidae in which i t was previously classified. Ardeirhynchus n. g. is distinguished from the most morphologically similar genus, Arhythmorhynchus Luhe, 1911, by the position of the male genital system, which occupies the posteri or 1/8-1/6 part of the trunk, the distribution of hypodermal nuclei in groups in the anterior part and in lateral rows along the length of t he posterior part of the trunk, a considerably shorter neck, minute tr unk spines and a terminal genital pore.