FURTHER STUDIES ON THE TREMATODE GENUS HIMASTHLA WITH DESCRIPTIONS OF H. MCINTOSHI N. SP., H. PISCICOLA N. SP., AND STAGES IN THE LIFE-HISTORY OF H. COMPACTA N. SP

The validity of species in the genus Himasthla is discussed; Echinostoma annulatum (Diesing, 1850) is transferred to Himasthla and H. tensa Linton, 1940 is suppressed as a synonym of H. elongata (Mehlis, 1831). A specimen from Nycticorax nycticorax, tentatively assigned to H. elongata, is very similar to H. secunda (Nicoll, 1906), which suggests the possibility that H. secunda may be a not-fully mature form of H. elongata. Three new species are described; H. mcintoshi from Numenius americanus americanus taken in Tooele County, Utah; H. piscicola, probably an accidental infection, from the South American fish, Arapaima gigas; and H. compacta from experimental infection of the herring gull, Larus argentatus. The life cycle of H. compacta has been traced; the asexual generations occur in Hydrobia minuta, the cercariae encyst in Mya arenaria and probably other mollusks.