4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.75 



Anterior end of gynaecophoric canal near acetabulum; genital pore of male 

 a short distance caudad of acetabulum ; intestinal ceca without diverticula ; 

 common cecum usually long; ovary pre-equatorial or post-equatorial in 

 position 5. 



5. Testes less than 10 in number; ovary oval Schistosoma, p. 4. 



Testes 18 to 20 in number; ovary spiral 6. 



6. Anterior end of gynaecophoric canal slightly caudad of the acetabulum ; oral 



sucker lacking in female ; ovary situated about one-third of the body length 



from the posterior extremity Austrobilharzia, p. 16. 



Anterior end of gynaecophoric canal cephalad of the acetabulum ; oral sucker 

 present in female; ovary pre-equatorial . Microbilharzia, p. 24. 



Genus SCHISTOSOMA Weinland, 1858 



Synmiyms. — G-ijnuecophorus Diesing, 1858, pp. 356-357 ; Bilharzia 

 Cobbold, 1859, p. 364 ; Thecosovm Moquin-Tandon, 1860, p. 342. 



Generic diagnosis. — Schistosominae : Preacetabular portion of male 

 short, cylindrical or nearly so; postacetabular portion widened and 

 with the edges inrolled ventrally forming a gynaecophoric canal. 

 Cirrus pouch absent. Seminal vesicle present, pretesticular. Testes 

 few in number (less than 10) , situated at the beginning of the gynae- 

 cophoric canal. Female filiform, longer than male. Ovary elong- 

 ated, in median line, usually caudad, rarely cephalad, of equator of 

 body. Laurer's canal absent. Eggs oval, or spindle-shaped, not 

 operculated, with terminal or lateral spine, or with a rudimentary 

 lateral spine, and ultimately containing a ciliated miracidium. 

 Parasitic in the blood vessels of mammals. 



Larva a furcocercous, apharyngeal, spinose cercaria without eye- 

 spots; with paired group of penetration glands around the acetabu- 

 lum ; penetration gland ducts opening at the anterior end of the oral 

 sucker and capped by hollow piercing spines; excretory system con- 

 sisting of four or five pairs of flame cells, one pair of which is located 

 in the base of the tail stem. Larval stages in snails. 



Type species. — Schistoscnna haematohimn (Bilharz, 1852) Wein- 

 land, 1858. 



KEY TO THE SPECIES OF SCHISTOSOMA 1 



1. Cuticle of male smooth ; testes seven in number ; ovary equatorial or post- 



equatorial ; egg 74/i to 106/t long by 60,11 to 80/^ wide, with rudimentary lat- 

 eral spine S. japonicuin, p. 7. 



Cuticle of male tuberculate and spiny ; testes more or less than seven in 

 number ; ovary usually post-equatorial, sometimes equatorial ; egg with 

 well-developed terminal or lateral spine 2. 



2. Intestinal ceca of male unite near equator, or cephalad of equator of body__3. 

 Intestinal ceca of male unite caudad of equator of body 4. 



1 Schistosoma incognitum Chandler, 1926, and S. faradjei are not included in this key, 

 as the adults of these spccios are unknown. jS'. faradjei is a name proposed by Walkiers 

 (1928) for a schistosome whose eggs were found in the feces of man in Africa, presumably 

 the Belgian Congo. No characters are given except that the egg is unarmed. For descrip- 

 tion of the egg f;f y. intoij nil 11)11 see p. 12. 



