STUDIES OX THE ECTOPAKASITIC TREMATODES OF JAPAX. 24; 



5. Tristomum rotundum, n. sp. 

 (PL XXIV, figs. 6-9.) 

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

 axis shorter, about 11.5 mm. by 13 mm., but sometimes a little longer 

 antero-posteriorly ; smooth both dorsally and ventrally ; with the 

 anterior border concave, and separated fi-om either lateral mar'gin by a 

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

 posterior border. Lateral margins entire, with numerous transverse 

 I'ows of chitinous bodies somewhat similar in form to those of 

 T. moloi^^ ; each row 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 body, 

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

 bodj'. Anterior suckers elliptical, of moderate size, attached to the 

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

 anterior border of the body. Posterior sucker circular, with its 

 hinder end scarcely reaching the posterior border 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 form 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, 9.16 mm. in length. Month small, between the 

 anterior suckers, at the plane of the beginning of the postex'ior third of 



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

 Nota preventiva. Op. cit., ser. 2, vol. Yll, 1888. p. 7il. 



