72 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.50. 



membrane. There is also a pair of well-developed conical adanal pa- 

 pillae. The tightly coiled posterior extremity of the male (fig. 81) in 

 this species makes any study of the bursa quite difficult. Associated 

 with this coiling habit is the presentation on the ventral surface, the 

 inner side of the coil, of several series of short parallel longitudinal 

 lines, commonly present, but apparently of a transient nature. The 

 spicule is slightly curved and difficult to measure, owing to the grad- 

 ual failure to complete chitinization in the proximal portion. Its ap- 

 parent range in length is from 85 to 175 jjl. The accessory piece is 

 flask-shaped and is 30 to 40 ^ long. The bursal membrane extends 

 from the adanal papillae to the postanal, swinging in toward the 

 body, and then forms a small membrane between the postanal papil- 

 lae and the thin terminal portion of the body. The distance from 

 the cloacal aperture to the posterior extremity of the body is 110 to 

 230 pi, of which the terminal portion posterior of the postanal papil- 

 lae makes up 75 to 135 ^ and the distance from the cloacal apertuie 

 to the postanal papillae makes up 85 to 100 [i. 



Female 9 to 18 mm. long, with a maximum thickness slightl}' ex- 

 ceeding 1 mm. The body terminates in the prolongation usual in 

 the female Oxyuris, and in favorable specimens this portion shows 

 markings somewhat similar to those of Oxyurls anibigua. However, 

 they are arranged in spirals and not in closed circles or annulations, 

 the number of turns being 18 to 24 in adults and fewer in young 

 specimens. The last spiral straightens out and extends on as a 

 straight line to the end of the body. The spirals appear to involve 

 the subcuticular epithelial structures primarily, and only involve 

 the cuticle in that it is apparently grooved on its inner surface to 

 receive this spiral. The head varies in diameter from 100 to 190 /*, 

 due partly to the difficulty of finding a definite position at which to 

 measure. The esophagus, exclusive of the esophageal bulb, measures 

 895 II to 1.065 mm. long by 170 to 185 ju, thick in mature specimens, 

 and the subspherical bulb measures 225 to 275 p. long by 290 to 345 {x 

 thick. The nerve ring is far forward on the esophagus, 95 to 155 ix 

 from the anterior end of the body. The excretory pore opens just 

 anterior of the vulva in the ventral line. The anus is a circular aper- 

 ture 1.72 to 2.58 mm. from the tip of the tail in mature specimens. 

 For a short distance back from the tail there are no distinctive 

 features. The middle portion of the tail shows the spiral markings 

 alread}^ mentioned, while the posterior portion of the tail terminates 

 in a thin prolongation devoid of markings. The position of the 

 A^ulva and vagina is distinctive of this and the following species 

 (fig. 82). The distal portion of the vagina extends through a cutic- 

 ular tube which projects out from the body of the worm, and the 

 vulva is located on the distal extremity of this tube. The vagina 

 is suspended in the tube by two mesenteries which extend along the 



