AiiT. 18 THE TREMATODE FAMILY SCHISTOSOMIDAE PRICE 6 



ent, caphalad of the genital pore. Body of male may be widened 

 caudad of the acetabulum and have the sides incurved vgntrally, 

 forming a gynaecophoric canal in which the female lies. Testes con- 

 sist of four or more follicles. Cirrus pouch present or absent. Female 

 more slender than male. Ovary elongate, sometimes spirally curved, 

 and lying cephalad of the cecal union. Laurer's canal present 

 or absent. Vitellaria extensive, extending from the distal pole of the 

 ovary to the posterior end of the body. Parasitic in the blood vessels 

 of birds and mammals. 



Ti/pe genus. — Schistosoma Weinland, 1858. 



KEY TO THE SUBFAMILIES OP SCHISTOSOMIDAE 



Females slender, more or less cylindrical in cross section; males larger than 

 fenrales, flattened, and with the lateral edges infolded, forming a gynaeco- 

 phoric canal ; intestinal ceca usually unite caudad of the equator of the body ; 

 testes situated cephalad of the cecal union Schistosominae, p. 3. 



Females similar to males in shape; males without well-developed gynaecophoric 

 canal ; cecal branches unite cephalad of the equator of the body ; testes situ- 

 ated caudad of the cecal union Bilharziellinae, p. 25. 



Subfamily Schistosominae Stiles and Hassall, 1898 



Sj/nom/m. — Schistosomatinae Stiles and Hassall, 1926, p. 96. 



Subfamily diagnosis. — Schistosomidae : Males flattened and with 

 the lateral edges of the body infolded ventrally to form a gynaeco- 

 phoric canal. Suckers present. Intestinal ceca long, usually uniting 

 caudad of the equator of the body; common cecum relatively short. 

 Testes situated in the anterior or posterior half of the body, always 

 cephalad of the cecal union. Females slender, threadlike, either 

 longer or shorter than the males. Uterus usually contains many eggs. 



I'ype genics. — Schistosoma Weinland, 1858. 



KEY TO THE GENERA OF SCHISTOSOMINAE 



1. Either male or female unknown 2. 



Male and female both known 3. 



2. Male unknown. Female slender, flattened; ovary spiral, in posterior third 



of body ; intestinal ceca unite near the posterior end of the body ; vitellaria 

 consist of a few scattered follicles between the cecal branches ; in birds. 



Paraschlstosomatium, p. 15. 

 Female unknown. Gynaecophoric canal well developed ; testes numerous, in 

 posterior third of body and cephalad of the cecal union ; in mammals. 



Heterobilharzia, p. 14. 



3. Testes 60 or more in number ; ovary spiral, in anterior third of body. 



Ornithobilharzia, p. 17. 

 Testes 20 or less in number; ovary equatorial or post-equatorial 4. 



4. Anterior end of gynaecophoric canal near the equator of body ; testes in 



two rows, at anterior end of gynaecophoric canal ; genital pore immediately 

 in front of the anterior testis ; intestinal ceca with short lateral diverticula ; 

 common cecum in both sexes short ; ovary pre-equatorial. 



Scliistosomatliim, p. 12. 



