STUDIES ON THE ECTOPAJRASITIC TREMATODES OF JAPAX. 241 



regiop between the intestinal trunks, mostly behind the ovary, 

 but extending also forwards on both sides about midway up the 

 ovary. Numerous vasa effercntia uniting in the median line and 

 forming a single vas deferens, which, with numerous convolutions, 

 proceeds forwards, keeping itself close on the left side of the 

 ovary, and reaching the front end of the latter here forms a long 

 loop "with its closed end directed forwards and towards the right ; 

 after this the vas deferens proceeds, still with complicated con- 

 volutions, for a short distance forwards, then bends towards the right; 

 and entering the penis at its base, finally opens into its cavity on 

 the top of a papilla, at a short distance from its apex ; its calibre 

 generally decreasing all along after the large loop at the front end 

 of the ovary. 



This species has a light flesh-red colour of its own, which does 

 not wholly disappear in alcoholic specimens. 



Habitat — Inner side of the gill-plates of Histiophonis sp. (Jap. 

 Kajiki). 



Locality — Misaki. 



Date — August 1891. 



2. Tristomum ovale, n. sp. 

 (PI. XXIII; PI. XXIV, figs. 1-5.) 

 Body oval, about 13 mm. long by 12 mm. broad or larger, 

 sometimes approaching more nearly a circle, with numerous, uniform- 

 ly scattered conspicuous papillae on the ventral surface, dorsally smooth. 

 Anterior border convex, separated from the lateral borders by a deep, 

 large notch on each side, at the apex of which is attached the anterior 

 sucker of either side; posterior end with a large obtuse notch. Lateral 

 margins entire, destitute of chitinous bodies. Anterior suclicrs of moderate 

 size, nearly circular, with numerous papillae on their inner margins. 



