FREE-LIVING NEMATODES 



491 



34 (31) Pharynx cyathiform then prismoid, ending behind very definitely; 



amphids distinct. . Ethmolaimus de Man. 



Genus of two known species, one European, one 

 American. Closely related to Chromadora, from 

 which it is readily distinguished by the narrow uniform 

 posterior portion of the pharynx, which is usually 

 surrounded by a comparatively distinct pharyngeal 

 bulb. 



Representative species. 



Ethmolaimus americanus Cobb 1914. 



<■ „ 2 5 10. . IS 'S4'" 90.3 . , 



Labial papillae, apparently 12. Onchus thumb- 

 shaped, forward pointing, attached to a distinctly 

 thickened rib of cuticula which extends from the lip 

 region back to the base of the pharynx, and is thicker 

 anteriorly than posteriorly. Fully developed ova are 

 nearly twice as long as the body is wide, and one-third 

 as wide as long. Form, size, and number of eggs un- 

 known. 



Habitat: Spring, Washington Country Club, Chevy 

 Chase, Md. 



Fig. 790. Ethmolaimus americanus. Lateral view of a 

 female, a, lips; b, minute dorsal and ventral pharyngeal 

 teeth; c, one of the four cephalic setae; d, amphid; e, 

 pharynx; /, nerve-ring; g, excretory pore; h, nerve cells; 

 i, cardiac bull); j, beginning of the intestine; k, renette 

 cell C? ) ; I, beginning of main portion of the intestine; m, one 

 of two pairs of unicellular organs of unknown significance; 

 n, cuticula; o, one of the cells of the intestine; p, subcuticula; 

 q and r, body cavity; s, vulva; i, nucleus of one of the 

 muscle cells; m, spinneret; v, one of the caudal glands; 



35 (30) Dorsal tooth minute, amphids circular. . . . Microlaimus de Man. 



Amphids well developed. 

 Genus of few species from Europe 

 and North America. 

 Representative species. 



Microlaimus fluviatilis 

 Cobb 1914. 



^ 15.5 W" 



'"43 '4'7" 



The eggs appear to be deposited be- 

 fore segmentation begins. Specimens 

 with one, and those with two, ovaries, 

 appear to be about equally numerous; 

 as no other difference has been detected, 

 they are included for the present under 

 the same name and description. 



Habitat: Maple River, Michigan. 

 Fig. 791. Microlaimus fluviatilis. 



I, lateral view of female; II, head of 

 the same. 



a, mouth opening; b, one of the six 

 cephalic papillae; c, one of the four cephalic 

 setae; d, one of the small pharyngeal teeth; 

 e, excretory pore; /, spiral amphid; g, 

 esophagus; k, nerve-ring; i, cardiac 

 bulb; j, preliminary portion of the in- 

 testine; k, renette cell; /, body cavity; 

 m. lumen of intestine; n, one of the cells 

 of the intestine; o, anus; p, flexure in 

 posterior ovary; g, uterus; r, blind end of 

 posterior ovar>'; s, one of the three caudal 

 glands; t, spinneret; u, eggs; v, vulva; 

 w, cuticula. (After Cobb.) 



