76 PROCEEDIISrGS OF THE NATIONAL MUSEUM vol.88 



in front of ventral sucker, to the left of the midline, the male aperture 

 surrounded by a strong, muscular, suckerlike structure. The ejacula- 

 tory duct passes dorsal to the ventral sucker, and the seminal vesicle 

 may extend for one-third or more of the distance between the ventral 

 sucker and ovary. Testes, two, one following the other, and touch- 

 ing, or separated by a short interval filled with follicles of the 

 vitellaria, usually rounded, circular or oval, or occasionally sub- 

 triangular in outline. Ovary at or near anterior border of first 

 testis, not lobed, circular to elliptical in outline. Vitelline reservoir 

 and shell gland in front of ovary ; seminal receptacle not seen, prob- 

 ably represented by early folds of uterus. Uterus between ovary and 

 ventral sucker ; the metraterm lies beside the ejaculatory duct, dorsal 

 to the ventral sucker, and opens at the anterior border of the genital 

 sucker in which the ejaculatory duct opens. Vitellaria dijffuse and 

 continuous from the posterior end to the posterior border of the 

 ventral sucker, or near it. The excretorj^ vessel extends from the 

 posterior end to the ovary ; ova about 0.05 by 0.03 mm. The average 

 dimensions of 24 ova, of distomes from 16 species of fishes, mostly 

 balsam mounts, were 0.053 by 0.029 mm.; maximum 0.083 by 0.033 

 mm., minimum 0.045 by 0.027 mm. Twenty-one of these distomes, 

 mounted in balsam, from 13 species of fishes, had an average length 

 of 1.88 mm., and an average breadth of 0.37 mm. ; maximum length, 

 3.38 mm., minimum, 0.94 mm. A living specimen slightly com- 

 pressed, measured 1.57 mm. in length and 0.85 mm. in breadth; 

 another, turgid, length, 2.1 mm., breadth, 0.35 mm. 



Hosts. — Common shad {Alosa sapidissima) , sand launce {A7n- 

 modytes americanus) ., common herring {Clupea harengus)^ sque- 

 teague {Oynoscion regalis), mackerel scad {Decapterus mucarellus) , 

 pinfish {Lagodon rhomhoides) ^ conger eel {Conger conger)., rusty 

 dab {Limanda ferruginea)., spot {Leiostomus xanthiorus) ., window- 

 pane {Lophopsetta maculata).^ kingfish {Menticirrhus saxatilis), sil- 

 ver hake (Merluccius bilinearis), goatfish {Mullus auratus)., toadfish 

 {Opsanus tau), rudderfish {Palinurichthys perciformis) ., summer 

 flounder {Paralichthys dentafys), four-spotted flounder {P. oh- 

 Jongus), spotted codling {Urophycis regiu^), codling {U. tenuis), 

 bluefish {Pomatomus saltatrix), alewife {Pomolohus pseudoharen- 

 gi(s), dollarfish (Poronotus triaca7ithus) , common gurnard {Merulinus 

 caroliiius), w^inter flounder {Pseudopleuronectes aniericanus), bonito 

 (Sarda sarda)., common mackerel {Scorriber scoTnbrus) ., comnion pipe- 

 fish {Syrictes fu.scus), puifer {Sphoeroides maculatus) ., southern 

 porgy {Stenotomus chrysops), taiitog {Tautoga onitis) , ciinner (Tau- 

 togolabrus adspersus)., round pampano {TracMnotus fdlcatus)., gog- 

 gler {Trachurops crwmenophthalma) . 



