Par.-in. 



.10. Lips diGtcndcri. , si^parabcd one from mioUior 



X. niamillntum Schuurmnns Sfcekhoven & TeunlG.'^on, 193^ 



Lips smooth, united 11 



11. Lips flattened; lip region not set off by a contriction 



X. index Thornc & Allen, 19^0 



Lips rounded; lip region set off by distinct constriction 12 



12. L = 2 mm.; "orgaji Z"""' in the females ^X. ebriense n. sp. 



L = 3-k ran.; without "organ Z" in the females 



X. diversicaudatum (Micholetzky, 192?) Thorne, 1939 



13. L = at least 8 mm. 



X. cylindricaudatujn Schuurmans Steckhoven & Teunissen, 1958 



L = at most 3 iron. lit 



lit. V = 5W ^X. americanum Cobb, 1913 



V = at most h7^ 15 



15. Length of tail one to one and one-half body with at anus; 



anterior ovary reduced ^X. krugi Lordello, 1955 



Length of tail longer than twice body width at anus; anterior 



ovary normal -I6 



16. Head truncate X- truncatum Thorne, 1939 



Head rounded 17 



""Organ Z" in the females has reference to a structure seen in the 

 genital tract of X. ebriense . This organ lies between the spermatheca 

 and the uterus. It is golbular in shape; very muscular; the lumen, 

 which opens wider in the center of the bulb, is bounded by a cuticular- 

 ized lining and possesses two to four moveable cuticularzied "teeth." 

 Generally, three "teeth" are seen, but it is difficult to distinguish 

 the exact number because of the thickness of the musculatu.re of the 

 orgp.n. Because of the unknown function of this organ M. Luc proposed 

 the nojne "organ Z." 



