STUDIES OX THK ECTOPAEASITIC TREMATODES OP JAPAX. 215 



swollen, giving rise to an elevated patch on the ventral side of the 

 body. Genito-intestinal canal arising from the oviduct a little nearer its 

 origin than the opening of the unpaired yolk-duct, proceeds forwards 

 and a little towards the right, and finally opens into the intestine. 

 Testes small, comparatively few in number, together forming a 

 triangular patch behind the ovary, between the two trunks of the 

 intestine ; not extending into the stalk-like portion. 



Habitat — Gill of Tclrodon sp. sp. (Jap. Kogome-fugu and Koyose- 

 fugii). 



Locality — Hagi. 



Date— August 1889. 



Although this species presents conspicuous differences from the 

 two foregoing species, there is no doubt that it is to be included in 

 the same genus, both from the form of the penis and its hooks and the 

 form of the sucker and its chitinous framework, as well as from some 

 other less significant points of similarity. As to the chitinous 

 frame-work of the suckers, it is to be remembered that, as already 

 mentioned in the anatomical part, that of the first pair presents 

 such a change in the relative position of the component pieces as 

 to have to be regarded as having undergone a rotation of 180° on its 

 own axis, the piece directed forwards in the other suckers being 

 turned backwards in this. In fact this species represents an aberrant 

 member of the sfenus. 



o^ 



y. Hexacotyle, Blainville. 



This genus was founded in 1828 by Blainville, and contains at present only 

 a single species, which was first met with by De la Eoche'' on the gill of Scomber 



1). De la Eoche — Sur deux auimaux vivants sur les branohies des poissons. X^ouv. Bull, 

 d. sciences d. 1. soo. PHlom., 1811., Xo. 14., 270-273. I cite this on the authority of Dujardin, 

 Diesing, and Braun. 



