2 PKOCEEDINGS OF THE NATIONAL MUSEUM vol. 75 



publications having a more or less limited circulation. The writer 

 has, therefore, attenipted to assemble descriptions of all the genera 

 and species, and has prepared keys which will aid in the identifica- 

 tion of these trematodes. Unfortunately many of the descriptions 

 are inadequate as they have been based in many instances on the 

 study of a limited number of specimens. Unless stated to the con- 

 trary the descriptions of known species have been compiled fronf 

 original sources. 



A few changes have been made in the classification of this group, 

 which appear necessary for proper coordination. A new subfamily, 

 Bilharziellinae, is proposed for those species resembling Bilharziella 

 polonica in form or organization. The genus Mdcrobilharzia Tra- 

 vassos is regarded as a synonym of Ornithohilharzia Odhner, the 

 type species, M. iimcrobUharzia^ apparently being congeneric with 

 Omithohilharzm intermedia Odhner. /Schistosoma homfordi Mont- 

 gomery and S. turkestcmiewih Skrjabin have been transferred to the 

 genus Ornithohllhcn-zia^ as neither of these species are congeneric 

 with Schistosoma haematohium^ (Bilharz) type of SchistosoTtia, and 

 both of them have characters of the genus Ornithohilharzia. 



The writer desires at this time to acknowledge his indebtedness to 

 the following for kindly placing specimens of schistosonies at his 

 disposal for study and comparison: Dr. C. W. Stiles, United States 

 Public Health Service ; Dr. J. H. Sandground, Harvard University ; 

 Prof. Edwin Linton, University of Pennsylvania ; Dr. Henry B. 

 Ward, University of Illinois; Capt, J. H. St. John, Army Medical 

 School ; and Lieut. Commander John Harper, Naval Medical School. 

 He also desires to express his appreciation to Dr. M. C. Hall, chief 

 of the zoological division, Bureau of Animal Industry, for suggestions 

 in the preparation of this paper ; to Dr. A. Hassall of the zoological 

 division for suggestions and material assistance in obtaining the liter- 

 ature; to Dr. Robert Formad of the pathological division, for mak- 

 ing translations of papers published in the Russian language; to Dr. 

 Paul Bartsch, of the United States National Museum, for supplying 

 correct names for the snail hosts; and to Dr. C. W. Richmond, of 

 the United States National Museum, for supplying correct names for 

 the birds from which schistosomes have been reported. 



Family SCHISTOSOMIDAE Looss, 1899 



Synon^/ms. — Schistosomatidae Poche, 1907, p. 126; Bilharziidae 

 Odhner, 1912, p. 58. 



Family diagnosis. — Trematoda: Sexes separate, Pharynx absent; 

 esophagus short, terminating posteriorly in a bifurcation to form 

 intestinal branches or ceca which join caudally at the cecal union to 

 form a single, slender intestinal cecum terminating near the posterior 

 end of the bodj'. Suckers present or absent ; acetabulum, when pres- 



