THE NEMATODE FAMILY GNATHOSTOMID.E. 



247 



Family Diagnosis. 



Gnathostomid.^; Railliet, 1895. 



Spiriiroidea*(?): with two large, trilobed, lateral lips, having 

 tlie cuticle of their inner surfaces thickened and usually raised 

 into longitudinal tooth-like ridges which meet or interlock with 

 those of the other lip. Tail of mile with more or less well- 

 developed lateral alte and two spicules. The vagina runs forward 

 from the vulva before giving off the two or four uterine 

 branches. Eggs with thin shells, ornamented externally with 

 fine granulations. 



Key to Subfamilies of Gnatliostomidse, 



A. Cuticle behind the lips distended into a head-bulb. 



by four submedian ballonets, a process from each 

 of which extends into the bod3'-cavity beside the 



oesophagus as a cerN'ical sac ■. GiiatJiosfomince (p. 254-). 



B. Head-bulb, ballonets, and cervical sacs a])sent Spirox/jiuce. 



SPIROXYIN.E, sul)fam. n.t 



These Gnatliostomid?e are without head-bulb, cervical sacs, or 

 ballonets. Their lips are characteristic. A deep cleft parts from 

 tlie body the whole thickness of the dorsal and ventral edges of 

 each, while the pulp of the middle lobe is separated from the 

 pulps of the adjacent lobes by indentations so deep as to produce 

 an appearance wdiich has been aptly likened by Schneider (1866, 

 p. 125) to the club on a playing-card (PI. I., tig. 2, PI. II. fig. 7). 

 Each lobe carries a papilla, the subdorsal and subventral papillae 

 having conspicuous and the lateral papillpe inconspicuous termin- 

 ations. The cuticle supporting the inner surface of each middle 

 lobe is greatly thickened, and projects anteriorly beyond the edge 

 of the lip as a sharp tooth-like prominence. 



lUie cuticle of the tail in the male is expanded laterally into 

 ala? aiid ventrally into vesicular swellings, which recall the 

 ventral fusion of the alje in Physalojjtera. There are eleven pairs 

 "of caudal papillaB J, of which two pairs are definitely ventral, one 

 pair lying in front of, the other behind, the cloacal opening; the 

 other nine are more lateral. Of these lateral papillae Nos. 2 

 and 5 are situated more venti-ally than the others ; six are post- 

 anal and three preanal, and in general the distension of the 



* Hall (1916) makes Railliet's superfamily Spiruroidea a synonym of Orley's 

 familj^ SpiruridiB, of the superfamily Filarioidea. If this system of classitication is 

 followed, there is no group of higher than family rank, embracing nematodes with 

 paired lateral lips, to which the present famib' can be assigned. We therefore use 

 the name of the superfamily Spiruroidea in this tsense. 



f For subfamily diagnosis, see p. 248. 



X Note. — Throughout our descriptions and in our figures we have numbered 

 the caudal papilbne of the mnle worms consecutivelj^ from the extremitj' of the tail 

 forwards — the first pair, or " No. 1," being that nearest to the tip. 



