444 FRESH-WATER BIOLOGY 



83 (83a) Rostellum entirely lacking. Scolex unarmed, very muscular. 



Family ANOPLOCEPHALIDAE Kholodkovsky 1902. 

 Not found in fresh-water hosts. 



83a (83) Rostellum present and armed with one or two rows of hooks. 



Family DILEPIDIDAE Fuhrmann 1907 . . 84 



With rostellum armed with single or double crown of hooks rarely in broken zig-zag row, 

 exceptionally rudimentary. Points of hooks directed posteriad. Suckers unarmed. Genital 

 pores marginal (see 84 just below). Sex organs in each proglottid simple or double. Uterus 

 sacculate or lobed, simple. 



Onchosphere with three membranes. Many genera chiefly found in birds, rarely in rep- 

 tiles or mammals. 



84 (85) Genital pores submarginal, dorsal, but never as far as half way 



from margin to median line. 



Trichocephaloides Ssinitsin 1896. 



Rostellum powerful with single crown of hooks. Genital pores unilateral, subdorsal. Cirrus 

 short and thick with long bristles; no seminal vesicle. Testes few, in posterior region of seg- 

 ment. Uterus sac-like; eggs few. Adults in birds. 



Few species in shore birds; parasites not reported from North America. 



85 (84) Genital pores distinctly marginal 86 



86 (93) Genital pores uniformly unilateral 87 



87 (88) Rostellum with single crown of hooks. Lateriporus Fuhrmann 1907. 



Rostellum armed with single crown of 12 to 16 hooks (120 to 170^ long), with long dorsal 

 and short ventral root, and well-developed blade. Proglottids broader than long. Genital 

 canals pass dorsal of longitudinal excretory vessels. Testes 12 to 30 in number, situated pos- 

 terior and lateral to ovary and vitellarium. Uterus sac-like, filling entire medullary paren- 

 chyma in terminal proglottids. Adults in birds. 



Five or more species, found in Europe in Anseriformes; not yet reported for North America. 



88 (87) Rostellum with double crown of hooks; rarely rudimentary and un- 



armed 89 



89 (92) No spines on base of cirrus 90 



90 (91) Testes not in front of but behind ovary and vitellarium. 



Dilepis Weinland 1858. 



Rostellum armed with double crown of hooks having long dorsal and short ventral root and 

 long blade. Inner longitudinal muscle layer consisting of numerous bundles. Proglottids 

 broader than long. Genital canals pass dorsal of the longitudinal excretory vessels and nerve. 

 Vas deferens coiled, seminal vesicle not developed. Testes in medullary portion typically 

 numerous (40^:0 50), but may be reduced in number (7). Uterus sac-like with few or numer- 

 ous outpocketings. Adults in birds and mammals. 



Many species from various birds including fresh-water types found in North America. 

 D. trans juga, from the spoonbill determined for North America by Ransom. D. unilaleralis 

 for the green heron by Stiles and Hassall, and by A. J. Smith; also for the little blue heron by 

 Leidy. 



91 (90) Testes very numerous, entirely surrounding the female glands. 



Cyclorchida Fuhrmann 1907. 



Rostellum armed with double crown of hooks, which have a very large dorsal root and small 

 hook portion. Genital canals pass between longitudinal excretory vessels. Cirrus-pouch 

 communicates with genital cloaca by narrow canal opening upon large papilla. Uterus ventral, 

 growing laterally between the excretory vessels into the cortical parenchyma and filling entire 

 proglottid. Adults in birds. 



In heron, crane, etc., in Europe. Not recorded for North America. 



