STUDIES ON THE ECTOPARASITIC TßEMATODES OF JAPAN. 245 



3. Tristomwn rotundinn, n. sp. 

 (PI. XXIV, figs. G-9.) 



Bodij oval in tlie state of perfect rest, with the antero-posterior 

 axis shorter, about 11.5 inm. hy 13 mm., Ijut sometimes a little longer 

 antero-posteriorly ; smooth both dorsally and ventrally ; ^vith the 

 anterior border concave, and separated from either lateral margin by a 

 deep, not very wide notch ; with only a shallow concavity on the 

 posterior border. Lateral margins entire, with numerous transverse 

 rows of chitinous bodies somewhat similar in form to those of 

 T. molce}^ ; each r(3w consisting of four or five bodies in the middle 

 part but diminishing in number towards both ends, beginning 

 just a little behind the anterior suckers and entirely absent for 

 a certain stretch on the concavity at the posterior end of the bod}^, 

 on both sides of which each row contains only a single chitinous 

 body. Anterior suckers elliptical, of moderate size, attached to the 

 body at the apices of the notches that divide the lateral from the 

 anteri<3r border of the body. Posterior such'r circular, with its 

 hinder end scarcely reaching the posterior 1j(3rder of the body, of 

 moderate size, with a diameter equal to about one-third the length of 

 the body proper ; with an elevated, central, regularly heptagonal area 

 and seven peripheral areas of the f jrm of an isosceles trapezoid ; the 

 latter all of equal size and the hindmost one occupying the median 

 line of the body. Hooks in one pair, solid, imbedded at the ends 

 of the posterior side of the central heptagon, thickened and pointed 

 at both ends, but with the free end sharper, of the form represented in 

 fig. 8, PI. XXIV, 9.1G mm. in length. Moulh small, between the 

 anterior suckers, at the plane of the beginning of the p<3sterior third of 



1). Parona e Perugia — lies ligusticae, VIII. Di alcuni trematodi cctopar. d. pesci marini : 

 Xota preventiva. Op. cit., ser. 2, vol. VII, 1888. p. Til. 



