292 



BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



and oval, each composed of 2 membranes, a dorsal and a ventral,, 

 transversely striated, united at their lateral edges and curved so 

 that they approach the median line, appearing thus almost as a 

 sheath. Six pairs of caudal papillae, of which 4 are preanal, 2 post- 

 anal. Spicules unequal and dissimilar, the left (fig. 356 d, e, and /) 

 700//, long, cylindrical in its anterior one-fourth, then shaped as a 

 gutter throughout its length until 42/* from the free end where there 

 is a hyaline, vesicular membrane enveloping it; the right spicule 

 (fig. 356 g, h, and i) 155/* long, its appearance different in different 

 views. 



Fig. 356. — Histiocephalijs tridens. a, Front view and 6, profile view of 

 head ; c, male tail ; d, anterior end ; e, posterior end, lateral view ; f, 



VENTRAL VIEW, LEFT SPICULE; g, RIGHT SPICULE, LATERAL VIEW; ll, RIGHT 

 SPICULE, DORSAL VIEW ; i, SHOWING NOTCHED APPEARANCE WHEN SPICULE RE- 

 MOVED FROM BODY. AFTER GEiNDRE, 1921 



Female 12.1 mm. long by 220/* wide. Anus 87/* from posterior end. 

 (1/138 of total length) ; posterior extremity conical, rounded at end. 

 Vulva salient, in anterior region of body, 2.07 mm. from anterior 

 extremity. Ovejector 1 mm. long, not differentiated into different 

 parts, directed posteriorly, gradually decreasing in thickness. Egg* 

 not mature in Gendre's specimens. 



Life history. — Unknown. 



Distribution. — Africa (French Guinea (Labe)). 



Genus YSERIA Gedoelst, 1919 



Generic diagnosis. — Schistorophinae (p. 284) : Mouth with 2 lips; 

 posterior to the lips a hood or crown with festooned edge. Lateral 

 papillae tricuspid. Female with vulva posterior to middle of body, 



Parasitic under mucosa of gizzards of birds. 



Type-species. — Yseria calif ornica Gedoelst, 1919. 



