A variety of Anopheles crucians, occurring in brackish water and differing rather markedly in larval characters from the common fresh-water form, has been recognized in the United States for several years. Root, in 1924, first suggested the occurrence of a second form, but the only difference mentioned at that time was in the number of palmate hairs (5 pairs in one, 6 in the other), which has not been confirmed by subsequent study. A few years later, in a key to the anopheline larvae of the United States, he included a “brackish-water race” of the species, with some additional characters. In 1932 Bradley first described the larval differences of the two forms and referred to them as the coastal and inland varieties. This coastal form has proved to be of rather common occurrence and has now been identified from various localities on the Gulf and Atlantic coasts from Louisiana to Maryland.