New avian trematodes of the genus Neodiplostomum.

External Features.-Body 2.I-2.8 mm. in length; forebody equal to or slightly longer than hindbody, separated by distinct constriction. Forebody flattened, 0.69-o.94 mm. across anterior quarter, and lateral margins curved ventrally in most specimens. Subterminal oral sucker, o.o6o-0o.o090o mm. in diameter, and acetabulum, 0.067-0.094 mm. in diameter, approximately equal in size; latter organ in about center of forebody. Holdfast organ, 0.28-0.53 mm. long, 0.23-0.47 mm. broad, elliptical in outline, about one-third length of forebody, between acetabulum and posterior end of forebody, with no portion hidden by ventral fusion of lateral body margins. No lateral sucking cups or specialized glands developed on forebody, but very fine spines, more numerous and larger at anterior end. covering forebody from oral sucker to region of holdfast organ. Hindbody roughly cylindrical but with widest diameter, 0.48-0.68 mm., at about middle of length. On its dorsal surface, near the posterior end (fig. 2), is the opening,, extremely variable in size, into the genital atrium; it is not marked by ridges, protuberances or other modifications of the body wall. Excretory pore, also on dorsal surface, opens posterior to genital atrium and very near posterior end of body. Digestive System.-Very short prepharynx, o.oo8-o.oio mm. long, connects mouth with pharynx, 0.052-o.o67 mm. long, 0.045-0.060 mm. wide. Length of esophagus, 0.067-0.1I2 mm., depends upon state of contraction or extension of anterior part of body. Intestinal ceca pass ventrally over reproductive glands in hindbody, curve dorsally around posterior limits of posterior testis, and terminate near genital atrium. They are narrower, 0.013-0.030 mm., in forebody and of larger diameter, 0.023-0.038 mm., in hindbody. Female Reproductive Organs.-Ovary, 0.125-0.156 mm. long, 0.195-0.234 mm. wide, 0.172-0.I90 mm. thick, in anterior quarter or anterior third of hindbody, usually a little nearer left than right side. Oviduct arises as narrow continuation of small conical projection on postero-dorsal surface of ovary, forming a small