PARASITIC FLATWORMS 409 



156 (153) Ovary lateral and slightly posterior to anterior testis but not 



directly behind it ^ 



157 (158) Genital pore at posterior end. . . Uucochloridium Carus 1835. 



Small distomes with compressed muscular body. Both suckers and pharynx large and p«jw- 

 erful. Esophagus short crura very slender, reaching nearly to posterior end Excretory 

 pore dorsal near caudal tip. Cirrus sac present. Laurer's canal present; rcccptaculum 

 wanting. Vitellana lateral, conspicuous, extracecal. Uterus in loops ascends on one side of 

 acetabulum, crosses body, and descends on the other side. Eggs small thick shelled 



In the cloaca of birds, not reported in North America. The larval' stage "in Sucdnva is a 

 si^orocyst which sends into the tentacles of the snail branches that are banded in <ol<,r and 

 are bitten off by birds Reported in a personal letter by Mr. Bryant Walker who found it in 

 Succmea ovalis in Michigan. 



158 (157) Genital pore ventral, median, just anterior to posterior testis. 



Hasstilesia Hall 1916. 



Very small oval distomes, nearly round in cross section. Skin 

 with minute spines in anterior region. Suckers .small, nearly 

 equal Pharynx and esophagus present, equal in length; crura 

 irregular, reach to posterior end of body. Excretory bladder 

 minute with two delicate lateral branches, (ienital pore ventral, 

 slightly dextral, midway from acetabulum to posterior end. Cir- 

 rus sac flask-shaped, large; cirrus long. Testes large, one in 

 extreme posterior region, nearly median, the other near center of 

 body on left. Ovary small, round, ventral to right intestinal 

 cecum, near anterior margin of posterior testis. \'itellaria lateral 

 in anterior half. Uterus in anterior region of body, moderately 

 developed, mostly pretesticular but with a single loop between 

 the testes. 



Eggs 13 by 20 ^£. 



Single American species. 



Fig. 710. Hasstilesia tricolor. HasstUesia tricolor (Stiles and Hassall) 1804. 



' ^^ ^^ ^''■' ^ In small intestine of 'Lepiis; abundant, Maryland. District of 



Columbia, Virginia. 



159 (64) Distomes of separate sexes. 



Family Schistosomatidae Looss iSqq. 



Adults parasitic in blood vessels of man, cattle, and birds; not yet found in North \merica 

 Cercariae very similar to those of this family occur in North .American snails. 

 Compare furcocercous cercariae 241 (246) in this key. 



160 (63) Special adhesive organ behind acetabulum, .\nterior region with 



holdfast organs usually distinctly separated from posterior 

 region with genitalia Suborder Holostomata Luhe. 



The genus Cyathocotylc without diflerentiated regions has not been nvordid in X.irih 

 America. 



Only family represented. 



Family HEiUSTOMiDAE Brandes 1888 . . i6r 



Distomes with body more or less distinctly divided into two regions. Anterior rcRion sp»K)n 

 or cup-shaped, serving as adhesive organ. Suckers poorly dcvelo|x-d. but with pi-culiar |>.)st- 

 acetabular sucking organ. Posterior region cylindrical t)r ovoid. Intestinal crura extend 

 to posterior end. Excretory bladder in form of subcutaneous network, (ienifal jxirc at 

 posterior end. Neither cirrus sac nor cirrus. Ovary and testes in series in |>osterior region. 

 Vitellana conspicuously developed. Uterus short with few, very large, thin-shelKil eggs. .\o 

 alternation of generations. Develop with intermediate host but without alternation of 

 generations. 



Parasitic in intestine of .Vmniota. 



