Pnr.-i;-. . K:)i 



7. Sninll species (I.6I6 mm.)j V = iiO.O;^, oesophagus short (b = 6) 



X. grande Steiner, 19llt. 



Lar^^P species (h.O mm.), V =^ GO.0%, oesophagus very long (b = 2) 



X. maJvrodorum (Vanha, 1893) Thorno, 1939 



3. Small species (0.8 iran.) X. obtusujn Cobb, 1939 



Large species (i.|.l mm.) 



X. rotu nd a turn Sch. Stekhoven & Teunissen, 1938 



9. Lip region expanded -X. lineum (Grube, 18[|.9) Thorne, 1937 



Lip region not expanded 10 



10. Head truncate X. truncatum Thorne, 1939 



Head more or less rounded, not truncate 11 



11. Length 3'h-h'O mm., or much larger (8.9U mm.) 12 



Length 2.60 mm. or less lU 



12. V = 38.9^ ^X. index Thorne & Allen, 1950 



V = ii7.8-ij8.0^ 13 



13. Length 8.9I; mm. 



X. cylindri ca uda turn Sch. Stekhoven & TeTinissen, 1938 



Length .UO rm. }C diversicaudatmn Qlicoletzky, 192?) Thorne, 1939 



lit. V = Sl.O-^k.0% ^X. gjnericanum Cobb, 1913 



V = 29.8-147.0^ 15 



15. Tail subconoid or digitate, not ventrally arcuate 16 



Tail distinctly elongated, more or less deeply ventrally arcuated-17 



16. Tail distinctly digitate (55.5 V- long), V = 39. li^ 



X. mammdllatum Sch. Stekhoven & Teunissen, 1938 



