44 NORTH AMERICAN 



about half way back to the vulva and contain six to ten developing ova ar- 

 ranged single file. The thin-shelled eggs, which are deposited before 

 segmentation begins, are fully twice as long as the body is wide and 

 about one-third as wide as long, and occur in the uteri one at a time. 

 Full-grown ova are ellipsoidal, and about one and one-half times as long 

 as the body is wide and about half as wide as long. 



55 

 .9 12.3 15.5 -M 86.6 



i.o mm. 

 i.i 1.4 1.4 1.5 1.6 



The tail of the male is like that of his mate in form. There are no sup- 

 plementary organs in front of the anus. The special male papillae charac- 

 teristic of this genus are located as follows : A single tapering, ventrally 

 submedian papilla a little in front of the proximal ends of the spicula, and 

 slightly farther back a lateral pre-anal papilla; a ventrally submedian papilla 

 as far behind the anus as that first described is in front of it ; a lateral papilla 

 twice as far behind the anus as that just described ; a ventrally submedian 

 papilla as far behind that just described as the latter is behind the previous 

 post-anal papilla; between the two ventrally submedian papillae just de- 

 scribed a group of minute subventral papillae ; near the middle of the tail, 

 on the slender part, two sublateral papillae. Most of these papillae are 

 slender, tapering, and one-third to one-half as long as the anal body diame- 

 ter. The two equal, yellowish, arcuate, acute spicula are about one and one- 

 fourth times as long as the anal body diameter. They taper pretty regu- 

 larly from near the proximal ends, where they are one-fourth as wide as 

 the corresponding portion of the body. The proximal ends diminish sud- 

 denly in diameter, and are then cephalated by expansion. Each expansion is 

 a rather strongly refractive, more or less bulbous piece of chitin. The acces- 

 sory piece is arcuate and about one-third as long as the spicula. It is par- 

 allel to and applied closely to the spicula. Its framework consists of two 

 distinct, nearly parallel parts. The ejaculatory duct is about one-fourth as 

 wide as the body. The blind end of the single outstretched testicle lies a 

 little farther behind the base of the neck than this latter is behind the an- 

 terior extremity. 



Habitat: Spring. Washington Country Club, Chevy Chase, Md. 

 Sublimate to balsam. 



PRISMATOLAIMUS, de Man, 1880. 

 Fig. 4, Plate III. 



14 



4. Prismatolaimus sternus, n.sp. i.i mm. 



1.2 1.5 1.9 1.9 1.5 



The moderately thin layers of the transparent, colorless cuticle are tra- 

 versed by about 550 transverse striae, resolvable with high powers into 

 rows of minute elements. There are no longitudinal striations. Scattered on 



