ON THE NEMATODE FAMILV GXATHOSTOMID^. 



245 



IG. A Revision of the Nematode Family Giiathostomids^. 

 By H. A. Baylis, M.A. Oxon., Assistant in the 

 Department o£ Zoology^ British Museum (Natural 

 History), and (yLAYTON Lane, M.D. Lond., Lt.-Col. 

 I.M.S. (ret.)*. 



[Received March 13, 1920 : Read April 13, 1920.] 

 (Submitted for Pablicatiou by permission of the Trustees of the ]3ritish Museum.) 

 (Text-figiues 1-40 ; Plates I.-VIII.t) 



Family GNATHOSTOMID^ ?. 



Cheiracantliklea Diesiiig (1861, p. 615). 

 Gnathostomidm llailliet"(1895, p. 1268). 

 Oxyuridce (in part) Railliet and Henry (1916, p. 114). 

 Grathostomiclce Skrjahin (1916, p. 972) [misprint]. 

 Heterakidce (in part) Seurat (1918, p. 25j. 



This family of nematodes was founded by Railliet to include 

 only the genus Giiathostoma Owen, Tiiough the family-nariie 

 appears constantly in text books on medical and veterinary 

 helmintliology, a comparative study of the genera and species 

 which appear naturally to fall into close relationship with 

 Gnatliostoma spijii(jerum, the t3'pe-species, lias never, to onr 

 knowledge, been undertaken. Such relationships have, in some 

 cases, been hinted at by previous writers. The genus Tcmqua 

 was tentatively referred to the family by Leiper (1908), while 

 certain species of Echinocephalus have been referi-ed by v. Linsto\^ 

 to Cheiracant/ms, which is a synonym of Giiathostoma. One other 

 genus, Spiroxys Schneider, 1866, the relationships of which have 

 never been decided with any precision §, we now propose to 

 include in this family, an inclusion wdiich appears 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 are obliged to be content with the 

 mere suggestion of their affinities. 



The cliief family characteristic is the possession of a pair of 

 large, fleshy, trilobed, latjcral lips. Each lip is provided externally 

 with three papill?e, while internally its cuticle is thickened and 



* Communicated by the Secretaky. 



t For explanation of tlie Plates see p. 310. 



X For fan'iily dia<;nosis, see p. 247. 



§ Railliet and Henry (191G) place it among the Oxyuridse, with Labicho'is as its 

 nearest ally. Seurat (1918) regards it as forming, with Camallanus, a subfamily, 

 Camallaninse, of tlie family Heterakida^. 



17* 



