n6. 



9o L = 0.8 mm; lip region nob set off by constriction, i.e. continuous 



. . ......... e . obtusum Thorne, 1939 



L = 3 nimj lip region set off by distinct constriction 



. . . = o yapoen.se Luc, 1958 



10. Lips distended, separated one from another 



mamillatvan Stekhoven & Teunissen, 1938 



Lips smooth, united 11 



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



., ijidex Thorne & Allen, 1950 



Lips rounded; lip region set off by distinct constriction 12 



12. L = 2 mm; "organ Z"-«- in the females ebriense Luc, 1950 



L = 3-U nim; without "organ Z"-}*- in the females 



,....,...,. diversicaudatum (Micoletzky, 1927) Thorne, 1939 



13. L = at least 8 mm , . , , cylindricaudatum Stekhoven & Teunissen, 1958 

 L = at most 3 nim. , . , lU 



lli. V = 5U^ americanum Cobb, 1913 



V = at most k7% . 15 



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



ovary reduced krugi Lordello, 1955 



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

 normal 16 



16. Head truncate truncatum Thome, 1939 



Head rounded 17 



17. Two-three pairs of caudal papillae 18 



At least four pairs of caudal papillae 20 



18. Two pairs of caudal papillae 19 



Three pairs of caudal oapillaa pratense Loos, 19U9 



19. A = 50-55; ventral pores setariae Luc, 1958 



A = 70; without ventral pores .... parasetariae Luc, 1958 



20. Four pairs of caudal papillae , campinense Lordello, 1951 



More than four pairs of caudal papillae 21 



21. V = kO-k^fo', six pairs of caudal papillae 

 elongatum Stekhoven & Teunissen, 1938 



V = U3-li7^ italie Meyl, 1953 



* "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 globular in shape; very muscular; the lumen, 

 which opens wider in the center of the bulb, is boiinded by a cntic- 

 ularized lining and possesses two to four moveable cuticularized 

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

 distinguish the exact nmiber because of the thickness of the muscla- 

 ture of the organ. Because of the unknown function of this organ M. 

 Luc proposed the name "organ Z." 



