ON THE NEMATODE FAMILY GXATHOSTOMID^. 245 IG. A Revision o£ the Nematode Family Grnathostomidse. Bj H. A. Baylis, M.A. Oxon,, Assistant in the Department o£ Zoology^ British Museum (Natural History), ;ind CJlayton Lane, M.D. Lend., Lt.-Col. I.M.S. (ret.)*. [Received March 13, 1920 : Read Ain-il 13, 1920.] (Submitted for Pablication by permission of the Trustees of the British Museum.) (Text-figures 1-40 ; Plates I.-VIII.t) Family GNATHOSTOMID.^ J. Cheiracanthidea Diesing (1861, p. 615). Gnathostomidce Railliet"(1895, p. 1268). Oxyuridce (in part) Railliet and Henry (1916, p. 114). Grathostomidce Skrjabin (1916, p. 972) [misprint]. Heterakidce (in part) Seurat (1918, p. 25). This family of nematodes was founded by Railliet to include only the genus Gnathostoma Owen. Though the family-name appears constantly in text-books on medical and vetei'inary helminthology, a comparative study of the genera and species which appear naturally to fall into close relationship with Gnathostoma spinigeru'm, the type-species, has nevei-, to our knowledge, been undertaken. Such relationships have, in some cases, been hinted at by previous writers. The genus Tanqua was tentatively referred to the family by Leiper (1908), while certain species of E chinocephalus h.a,ye been referred by v. Linstow to Cheiracanthus, which is a synonym of Gnathostoma. One other genas, Spiroxys Schneider, 1866, the relationships of which have never been decided with any precision §, we now propose to include in this family, an inclusion which a.ppears to necessitate a division of the family into two subfamilies. Certain other forms seem, from their existing descriptions, to be closely related (see p. 305), but in the absence of opportunities for re-examination of specimens we wre obliged to be content with the mere suggestion of their affinities. The ciiief family characteristic is the possession of a pair of large, fleshy, trilobed, lateral lips. Each lip is provided externally with three papillte, while internally its cuticle is thickened and * Communicated by tlie Secretary. f For explanation of the Plates see p. 310. J For familj' diagnosis, see p. 247. § Railliet and Henry (1916) place it among the Oxyuridse, with Lahiduris as its nearest ally. Seurat (1918) regards it as forming, with Camallanus, a subfamily, CamallaninEe, of the familj' Heterakidas. 17*
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