216 



S. GOTO. 



thynnus and described by him under the name of Poli/stoma thynni. Later it 

 was described under tlie name of Folystoma ditplicata by Kudolphi') in las 

 "Entozoorum synopsis." Tlie diagnosis 2) given by Blainville is as fol- 

 lows : " Corps ovale, diiprime, continu ou non articule, compose de deux parties ; 

 une anterieure, bien plus petite, subcylindrique, ridee ; I'autre posterieure, beaucoup 

 plus grande, ovale, alongee, deprimee et bordee inferieurement par trois paires de 

 ventouses, armees a I'interieur de deux petits crochets opposes. Tete petite, pen 

 distincte, portant la bouche h son extremite. Anus dorsal a la jonction du cou et du 

 corps. Orifice des organes de la generation au meme endroit en dessous." The 

 "anus " above referred to is probably the opening of the vagina, which is very con- 

 spicuous on a surface view. In his " Histoire naturelle des Helminthes " D u j a r d i n^^ 

 gives the following diagnosis of the species, for which he adopts the name given it by 

 Eudolphi: "Corps grisiitre, mou et Hsse, longde 12 ii 16 mm., large de 3.4 mm., et 

 elliptique au milieu, retrc-ci en avant, elargi en arriere, oii se trouvent les six 

 ventouses rangees transversalement, avec deux papilles intermediaires ; — ^boueho 

 terminale ; — ventouses bivalves, soutenues par plusieurs pieces cornees qui, en 

 se rapprochaut les font paraitre divisees (diqilicataj" a description differing only 

 in a few points from that of Blainville, but in many respects more incomplete. 

 Biasing'') in his "Systema helminthum" erected for the species a new genus 

 Playiopeltis, with the following diagnosis : " Corpus elongatum depressum. Caput 

 corpori continuum. Os Acetabula ventralia octo in corporis parte dilatata mar- 

 ginalia, serie simplici disposita, elliptica planiuseula, margiuata, singula acetabulum 

 transverse ellipticum margine involutum, centrali minus, includentia. Genitalia 



externa Porus excretorius Piscium marinorum ectoparasita." A new 



addition to our knowledge of the genus contained in the above is the correct ascer- 

 tainment of the number of posterior suckers (eight), the innermost pair of which is 



]). Eudolphi — Entozoorum synopsis, 1819. pp. 125 & 438. Cited on the authority of 

 Dujardin, Diesing, and Braun. 



2). BlaiuvUle— Dictionnaire des sciences naturelles. T. 57, 1828. p. 570. PI. XXVII, fig. 1. 

 Cited on Braun's authority. 



3). Dujardin— Histoire naturelle des helminthes, 1845. p. 318. 



4). Diesing — Systema helminthum, p.4l6. The diagnosis given in his " Revision der 

 Myzhelminthen " (p. 363) seems to me scarcely an improvement. 



