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* 



