STUDIES OX THE ECTOPAEASITIC TREMATODES OF JAPAX. 223 



O. emaifjinataj were desBiibecl by Olsson'); and finally iu 1890 a fourth species 

 (O. Prenanti) was added to the genus by St.-Eemy^). Besides these there is 

 according to Diesing') another species not yet described but mentioned by Wag e- 

 n e r in a note to a paper of his published in " Naturk. Verhand. Harlem, XIII," 

 as living on the gill of Scijmnus ainosi. This species is not mentioned either by 

 Braun or St.-Eemy, and I am not sure whether it will prove to be identical 

 with some one of the species already described, or to belong to quite another genus. 



The original diagnosis of Diesing is as follows ; "Corpus lineari-lanceolatum 

 depressum, utrinque angustatum. Caput corpore continuum. Os subterminale. 

 Acetabula sex disco elliptico extremitati eaudali supra adnato, biseriatim immersa, 

 hemisphaerica, margine uncino simplici inferna adnato apice libero armata. 



Aperturae genitales Porus excretorius in apice eaudali. — Piscium marinornm 



ectoparasita." This was improved in his " Eevision " *'> as follows : " Corpus 

 lineare-laneeolatum depressum, aj>pendiciilo caiulali j)oatico. Caput corpore con- 

 tinuum. Os subterminale. Acetabula sex, lamellae ellipticae, extremitati corporis 

 posticae subtus adnatae, biseriatim immersa, hemisphaerica, margine uncino simplici 

 inferne adnato, apice libero, armata. Androgyna ; aperturae genitales postpositae 

 ventrales antrorsum sitae, medianae ; penis vaginatus ante aperturam femineam 

 situs. Pori excretorii duo in appendice eaudali, terminales. — Tractus intestinalis 

 bicruris, coecus. — Ovipara ovulis utraque extremitate appendiculo filiformi in- 

 structis. — Piscium marinorum ectoparasita " — a diagnosis which has been repeated 

 in its essential points by subsequent writers, but which requires some modifications 

 in accordance with the facts already mentioned in the anatomical part of the 

 present paper. It has moreover been stated that in some species the caudal append- 

 age does not bear any hooks near its extremity. This statement sounds somewhat 

 anomalous to me ; but as I am not able to reexamine the species iu question, I shall 

 leave the statement as it stands, and give the generic diagnosis as follows : 



Body elongated, very thick, narrow towards both 

 ends; anterior end blunt, and with a sub-ellipsoidal sucker 



1). Olssou — Bidrag til Scaadinaviens helminthfauua. Kgl. syenska vetensk. Acad. Handl. 

 N. F. XIV, 1878. p. 35. Cited on the authority of Braun and St.- Remy. 



2). St.-Remy — Siir une espeoe nouvelle de Polystouiien du genre Onchocotyle Dies. Rev. 

 biol. d. Nord de la France. III. ann., 1890. p. 41. Cited on the combined authority of Braun 

 and St.-Eemy. 



3). Diesing— Revision der Myzhelminthen, 1858, p. 371. 

 4). Diesing— Revision, p. 370. The italics are mine. 



