Studies on Larval Trematodes Infecting Freshwater Snails in London (U.K.) and Some Adjoining Areas:Part I.—Echinostome Gercariae

Seven species of Echinostome cercariae are recorded from London ponds and rivers. Two of these,C. Z. ReesandC. echinoparyphii recurvatiMathias have already been described from other parts of Britain. The rest are new species.C. londonensisn.sp.,C. deficipinnatumn.sp. are thirty-seven spined andC. essexensisn.sp. has forty-nine spines.C. hamptonensisn. sp., andC. thamesensisn. sp. are both large-tailed Echinostome cercariae, with twenty collar spines. The possibility of using snails as second intermediate hosts byC. hamptonensis, a large-tailed Echinostome cercaria is shown to be highly improbable. The classification of Echinostome cercariae is discussed.