. Fresh-water biology. Freshwater biology. 4o8 FRESH-WATER BIOLOGY The common European species (D. dendriticum, the old Distoma lanceolatuni) is said by Leidy to be frequent in sheep in several western states, but Stiles and Hassall report it as ap- parently not in North America. I have never seen a specimen collected here. Confusion with Opisthorchis and similar forms is common in earlier records. North American genus. . Halipegus Looss 1899. Moderate sized distomes with muscular body, round in cross-section, and powerful suckers. Pharynx large, esophagus short, crura extending to posterior e
. Fresh-water biology. Freshwater biology. 4o8 FRESH-WATER BIOLOGY The common European species (D. dendriticum, the old Distoma lanceolatuni) is said by Leidy to be frequent in sheep in several western states, but Stiles and Hassall report it as ap- parently not in North America. I have never seen a specimen collected here. Confusion with Opisthorchis and similar forms is common in earlier records. North American genus. . Halipegus Looss 1899. Moderate sized distomes with muscular body, round in cross-section, and powerful suckers. Pharynx large, esophagus short, crura extending to posterior end. Genital pore close to pharynx. No cirrus. Testes lateral, near posterior end, symmetrical. Ovary close behind right testis; vitellaria just behind ovary and composed of group of 4 to 5 large folUcles on each side. Uterus in crowded transverse coils, filling almost entire body. Eggs extremely numer- ous, small, with long polar filament. In mouth and pharynx of amphibia. North American species. . Halipegus occidtmlis Staflford 1905. In mouth and eustachean tube of Rana calesbiana; Canada, Massachusetts. 152 (149) Ovary between testes. I S3 I S3 (156) Ovary median or nearly so, hence directly behind anterior tes- tis. 154 iS4 (155) Genital pore between acetabulum and pharynx. Sphaerostoma Stiles and Hassall 1898. Small distomes with actively mobile, powerful anterior region and broad posterior region. Suckers powerful. Pharynx present, esophagus long, crura reach into caudal end, Cirrur sac large, cirrus muscular. Testes separate, anterior one near acetabulum on right, posterior one near caudal tip, median. Ovary intermediate but sUghtly to left of median line, Vitel- laria extensive, lateral, from pharynx to posterior end. Uterus in few coils between posterior testis and acetabulum. With few, large eggs. This genus has not yet been reported from fresh-water fishes in North America. Linton has found it in marine fishes in the Woods Hole region and it is common in Europe in Cyp
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