This parasite was discovered in April, 1876, at Zagazig, Egypt, by Sonsino. He collected 35 specimens from the abdominal veins of oxen and sheep and from the portal vein of a bull. He stated that the parasite is larger than S. hæmatobium and has the same general aspect and characters, but is easily distinguished by the shape of the eggs. The eggs of S. bovis are .16 mm.-.18 mm. long and .04-.05 mm. broad, fusiform in shape and very much narrowed at the extremities. The pole which, in the oviduct, is turned away from the vulva, always carries a pyriform spine.