DESCRIPTION OF A NEW SPECIES OF MARITREMA NICOLL 1907, MARITREMA ARENARIA, WITH STUDIES OF THE LIFE HISTORY CHARLES E. HADLEY AND RUTH MARION CASTLE (From the Montclair State Teachers College, Montclair, N. /.; Vassar College, Poughkeepsie, N. Y.; and the Marine Biological Laboratory, Woods Hole, Mass.) HISTORICAL The genus Maritrema, established by Nicoll in 1907, includes a num-ber of small distomes, most of them intestinal parasites of shore birds. The most characteristic morphological feature of the group is the ring-like arrangement of vitellaria, which almost completely encircle the body posterior to the testes. Other features of diagnostic value are the ap-proximately equal size of the suckers ; the exit of the male duct at a small papilla located near the acetabulum, and continuous with a well-developed cirrus sac ; and restriction of the voluminous uterus to the posterior third of the body. The species of Maritrema described to date are as follows : M. gratiosum Nicoll, 1907. M. lepidum Nicoll, 1907. M. humileNicoll, 1907. M. lingnilla Jagerskiold, 1909. M. subdolwn Jagerskiold, 1909. M. nicolli Travassos, 1921. M. pulcherrima Travassos, \929a, b. M. sachalinicuin Schumakowitsch, 1932.. M. acadlae Swales, 1933; Ciurea, 1933. M. rhodanicnm Carrere, 1936. M. ovata Rankin, 1939&. ^ An apparently new species of Maritrema was recovered from the in-testine of the black-headed gull by Rothschild (1938), who indicated in a footnote that a description of the form was forthcoming. M. obstipuin (Van Cleave and Mueller, 1932 ; Mueller, 1934 Syn. Microphallus ubstipiun), M. medium (Van Cleave and Mueller, 1932; Mueller, 1934 Syn. Microphallns medium), and M. nettae (Gower, 338
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