30 



BULLETIN 69, UNITED STATES NATIONAL MUSEUM. 



uterine organ (figs. 21, 22, par. at.) Avhicli behind is in immediate 

 relation with the anterior end of the uterus. The para-uterine organ 

 when fully developed extends forward to the anterior end of the 

 segment in a slightly tortuous course. Its wall is 5 to lOfx thick, 

 composed in large part of muscular elements, and its cavity before 

 the eggs pass forward into it from the uterus is filled with a finely 

 fibrous mass. The eggs are oval, with a thin outer membrane 36 

 to 40/x in diameter, a thicker middle shell 24 to 27/x in diameter, and 



par. ut._A— - — > 



c.p, 



va&. 



1 mm. 



Pig. 22. — Rhabdojietka xullicollis : Geavid segment. 

 c. p., CinEus POUCH, pur. ut.. Para-uterine okgan. ut., 

 Uterus, rag.. Vagina. 



a thin inner membrane closely enveloping the oncosphere, which 

 measures 18|U, in diameter. When the eggs first enter the uterus 

 they are surrounded by a single membrane, the others developing 

 later. 



RHABDOMETRA SIMILIS, new species. 

 Figs. 23-26. 



This species is based on specimens (from the collection of H. B. 

 Ward, deposited in the U. S. National Museum Helminthological 

 Collection, No. 7236) collected from a rain crow {Goccyzus america- 

 nus) in Nebraska. No heads were present in this material, but the 



