186 PROCEEDINGS OF THE NATIONAL MUSEXJM vol. loi 



rior and middle body thirds ; it measures 0.38 to 0.82 mm. in diameter. 

 Katio of diameter of oral sucker to acetabulum varying from 1 : 1.3 

 to 1 : 1.9. Prepharynx absent. Pharynx globular, 0.08 to 0.23 mm. 

 in diameter. Esophagus narrow, usually slightly wavy, 0.08 to 0.40 

 mm. long, bifurcating one-half to two-thirds the distance from oral 

 sucker to acetabulum. Ceca of medium width, straight to slightly 

 wavy, passing outside of lateral margins of testes to terminate about 

 midway between ends of vitellaria and posterior end of body. Cere- 

 bral ganglion conspicuous, ventral to posterior margin of pharynx. 

 Excretory pore terminal. Excretory vesicle (fig. 39, h) simple, tubu- 

 lar, extending anteriorly through about one-third of body length, 

 receiving a common collecting tubule from each side. Each common 

 collecting tubule rather voluminous, passing anterolaterally between 

 testes and acetabulum to divide into an anterior and posterior main 

 collecting tubule at level of equator of acetabulum. Each anterior 

 and posterior main collecting tubule on each side of body giving rise 

 to three short accessory tubules. Each accessory tubule branching 

 into a dorsal and ventral capillary tubule, each of which terminates 

 in a single flame cell. Flame cell pattern 2 [(2+2+2) + (2+2+2)]. 

 Genital pore median, at level of pharynx. Testes rounded, 0.09 to 

 0.45 mm. in diameter, situated directly opposite with their fields widely 

 separated and their zones immediately behind or overlapping that of 

 acetabulum. Vasa efferentia arising from anteromedial margin of 

 testes and passing anteriorly and medially to unite as they enter cirrus 

 sac. Cirrus sac elongated, 0.24 to 0.73 mm. long by 0.09 to 0.34 mm. 

 wide, containing a convoluted seminal vesicle, ejaculatory duct sur- 

 rounded by prostatic gland cells and eversible cirrus; it usually lies 

 entirely in front of acetabulum. Ovary round to transversely oval, 

 0.10 to 0.36 mm. in greatest diameter, situated submedially, relatively 

 far from testes. Seminal receptacle globular, located dorsal or pos- 

 terior to caudal margin of ovary. Mehlis' gland situated medially to 

 seminal receptacle. Latirer's canal present. Vitellaria composed of 

 numerous medium-sized oval follicles, mainly extracecal, extending 

 posteriorly from within testicular zones for a distance of 0.82 to 2.11 

 mm. (about two-thirds distance to posterior end of body). Vitelline 

 ducts arising from about middle of vitellaria. Uterus convoluted, 

 filling most of posttesticular region of body, then following an un- 

 dulating course to genital pore. Mature ova dark brown, 9,7 fi to 33/* 

 long by 17fi to 23/i wide, fully embryonated with oviposited. Mira- 

 cidium symmetrical, ciliated^ possessing a stylet and with two large 

 oppositely situated vesicles in the posterior half of body; vesicles 

 containing highly refractile granules. 



Hosts. — Quiscalus quiscula aeneus Ridgway (type), Quiscalus 

 quiscula quiscula (Linnaeus), Cassidix mexicanus prosopidicola 



