THE ROUNDWORMS OF DOMESTIC SWINE. 43 



Family Strongylidae. Nematoda: Head with eix more or less distinct circu- 

 moral papillae. Males with a more or less well-developed bursa, 

 each lateral lobe of which is usually supplied with six supporting 

 rays. Spicules equal or subequal. Vulva may be anterior to the 

 middle of the body, but is usually posterior. Oviparous. De- 

 velopment, so far as known, direct without intermediate host. 

 Subfamily Strongylinae. Strongylidse: Buccal capsule well developed. 

 Eggs in the process of segmentation at the moment of oviposi- 

 tion. Embryo nearly always rhabditiform and development di- 

 rect. Parasitic in the alimentary canal; exceptionally in the res- 

 piratory system. 



Genus (Esophagostomum. Strongylinae : Head 75 p or more in diam- 

 eter; buccal capsule small. Cuticle surrounding the mouth usually 

 inflated to form a ringlike mouth collar. Bursa of male with two 

 lateral lobes united by a smaller median lobe. Spicules more than 

 0.5mm. long, slender, tubular, pointed ; gubernaculum present, but 

 not conspicuous (Esophagostomum dentatum. 



Genus Globocephalus. Strongylinse: Buccal capsule cylindrical, 

 larger in diameter than the thickness of the body, supported by 

 two chitinous rings one at the anterior end of the capsule, the 

 other at the posterior end. The rings are joined by four chiti- 

 nous longitudinal bands Globocephalus longemucronatus. 



Genus Crassisoma. Strongylinse: Buccal capsule oval, smaller in 

 diameter than the thickness of the body, supported by eight longi- 

 tudinal thickenings of the cuticle, and a chitinous ring on the 



inside of the capsule Crassisoma urosubulatum. 



Subfamily Trichostrongylinse. Strongylidae : Buccal capsule absent or 

 slightly developed. Eggs generally segmenting at the time of 

 oviposition. Embryo rhabditiform and development direct. 

 Parasitic in the alimentary canal. 



Genus. Undetermined Strongylus rubidu*. 



Subfamily Metastrongylinse. Strongylidse : Buccal capsule absent or 

 slightly developed. Eggs in various stages when oviposited. 

 Embryo rhabditiform. Evolution unknown, perhaps requiring an 

 intermediate host. Parasites of the respiratory or circulatory 

 system. 



Genus Metastrongylus. Metastrongylinae: Mouth with six lips. 

 Postero-lateral ray much reduced or absent. Dorsal ray and 

 externo-dorsal rays slender, the others thick. Two very long 

 spicules. Vulva close to the anus. Eggs with well-developed 

 embryos. Parasitic in the bronchi and trachea. 



Metastrongylus apri. 



o , , ., Metastrongylus brevivaginatus. 



bubfamily not determined. 



Genus Stephanurus. Strongylidae: Anterior extremity truncated; 

 mouth suborbicular, limited by a chitinous ring furnished with 

 teeth. Caudal bursa of male with many lobes. 



Stephanurus dentatus. 



1 See footnote 1 on p. 39. 



