PROC. BIOL. SOC. WASH. 93(4), 1980, pp. 1035-1079 REVIEW OF HYSTEROTHYLACIUM AND IHERINGASCARIS (BOTH PREVIOUSLY = THYNNASCARIS) (NEMATODA: ANISAKIDAE) FROM THE NORTHERN GULF OF MEXICO Thomas L. Deardorff and Robin M. Overstreet Abstract. — The genus Hysterothylacium Ward and Magath (type-species H. brachyurum Ward and Magath) is resurrected to include those species previously considered as members of the junior synonym Thynnascaris Dollfus and others described in the genus Contracaecum Railliet and Henry that mature in fishes. Iheringascaris Pereira is resurrected for /. inquies (Linton), the senior synonym of /. iheringascaris Pereira. Consequently, we establish 47 new combinations plus present lists of species that may later be shown to be members of Hysterothylacium. At least six species of Hys-terothylacium [H.fortalezae (Klein), H. incurvum (Rudolphi), H. chaunaxi (Olsen), H. reliquens (Norris and Overstreet), H. ogcocephali (Olsen), and H. corrugatum sp. n.] occur in the Gulf of Mexico, and morphological data and a key are presented for these. Hysterothylacium corrugatum infecting the swordfish from the Atlantic and Pacific oceans can be characterized primarily by having modified preanal annules ventrally in males and a tail without ornamentation in conjunction with lacking both deep interlabial grooves and flaring cervical alae. Several adult nematodes infecting the digestive tracts of finfishes have been described as species of Thynnascaris Dollfus, 1933 or Contracaecum Railliet and Henry, 1912. Species of Contracaecum sensu stricto, however, mature in birds and mammals. Reexamination of Hysterothylacium brachy-urum Ward and Magath, 1917, as discussed below, reveals it to have the same generic features as species of Thynnascaris. Before the genus Thyn-nascaris gains more acceptance, especially in light of potential public health significance of some species (Petter, 1969a, b; Norris and Overstreet, 1976; Norris and Ebert, MS in preparation; Overstreet and Meyer, MS in prep-aration), we wish to establish the priority of Hysterothylacium Ward and Magath, 1917 and Iheringascaris Pereira, 1935, transfer known species, and provide data on species of those genera from the Gulf of Mexico. Most specimens that we collected were removed from hosts, fixed in glacial acetic acid, stored in a solution of 5 parts glycerin and 95 parts 70% ethyl alcohol, and examined in lactic acid or in glycerin after the evaporation of the alcohol. A few others from hosts in museums had been fixed in
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