TRICHONEMINAE 155 



collar and usually with appendages. Spicules terminating in 

 double hooks. Vulva close to anus. Uterine branches parallel. 



Hab. Large intestine of Equidae. 



Genotjrpe : T. [C ylicostomum] longibursatum (Yorke & 

 Macfie, 1918). 



Cobbold, 1874, Veterinarian, London, xlvii, 6, 237 ; Mehlis, 

 1831, Isis (v. Oken), 79; Looss, 1900, Centralbl. f. Bakt. (I), 

 xxvii, 150; 1902, Rec. Egypt. School Trap. Med., Cairo (1901), 

 36, 86; Railliet, 1901, Echo vet., Liege, xxxi, 40; Yorke & 

 Macfie, 1918, Ann. Trap. lied. Parasit., Liverpool, xi, 400 ; 

 Ihle, 1922, Rep. Comm. Sclerostom. Holland, I, Zool. i, 37 ; Le 

 Roux, 1924, Journ. Helminthol. ii, 115. 



Since Le Roux (1924) has made use of Trichonema, there is 

 no alternative but to acknowledge the probable correctness of 

 that name. So far as the genotype is concerned, Le Roux 

 points out that S. tetracanthus Mehlis, 1831, cannot be identi- 

 fied with certainty, and therefore ceases to be a valid t3rpe. 

 He designates T. longibursatum as type of the genus, since he 

 believes that Miiller's fig. 12 in Icones Zool. Dan., ii (1780), 

 refers to a male of this species, and since he considers this to 

 be the most common species in the horse in Europe. This 

 definite designation of a type is undoubtedly to be preferred 

 to further speculation concerning the probable identity of 

 8. tetracanthus Mehlis. 



This genus has been divided into the following subgenera : 



la. Subgen. Trichonema Le Roux, 1924. 



Syn. Cylicostephanus Ihle, 1922. 



Mouth-opening circular. Mouth-collar depressed. Buccal 

 capsule usually long and cylindrical, or somewhat narrowed 

 anteriorly. The elements of the internal leaf-crown are short 

 rods, situated in the immediate neighbourhood of the anterior 

 margin of the capsule. Tail of female usually straight. 



Type-species : T. {Trichonema) [Cylicostomu7n] longibursatum 

 (Yorke & Macfie, 1918). 



Yorke & Macfie, 1918, ^;m. Trop. Med. Parasit., Liverpool, 

 xi, 400 ; Ihle, 1922, Rep. Comm. Sclerostom. Holland, I, Zool. 

 i, 77 ; Le Roux, 1924, Journ. Helminthol., ii, 118. 



16. Subgen. Cylicostomum Ihle, 1922. 

 External leaf-crown consists of eighteen to twenty-four, 

 mostly pointed, elements. Internal leaf -crown composed of 

 thin, triangular, radially-disposed plates, whose origin extends 

 backwards on to the internal surface of the buccal capsule 

 some distance from its anterior margin. A " problematical 

 structure " is present in the mouth-collar. Buccal capsule 

 rather short, thick- walled. Tail of female straight or slightly 

 bent dorsally. 



