222 s- ^^^'fo. 



front of the constriction which divides the middle from the posterior 

 portion of the body. 



Habitat — Gill of Thynnus sp. [Jap. Mebachi-maguro). 



Locality — Misaki. 



Date— August 1891. 



Although we have no adequate description of Hexacotyle thynni, 

 de la Roche, the only species of the genus hitherto described, I believe 

 there is scarcely any doubt that the two species here described are new. 

 Thus, in the first place, the general form of the body of both the species 

 differs from that of H. thynni as figured by St.-Remy '^ and Dies- 

 ing^^; and in the second place, according to the statement and figure 

 of the former writer, the larger pair of hooks is situated in front of 

 the other, which is not the case in either of the species here described. 



VI. Onchocotyle, Diesing. 



This genus is due to Diesing who erecteil it in Lis " Systema lielmiutlinm " 

 (1850) for an ectoparasite found for the first time (1829) by Kulm^) on tlie gill of 

 Sqiialiis cattdiis and described by him under the name oi Pohjstoiim cqipendiculatum. The 

 same species was afterwards redescribed more at length by Nor dm an n*), Thaer^)' 

 P. J.v. Beneden^), and Taschenberg^^. In 1853 P.J. v. Beneden*) 

 added a new species fO. borealisj ; in 1878 two more new species CO. ahhreviata and 



1). St.-E,einy— Synopsis. PI. X, fig. 22. 



2). This I cite on the authority of Braun, in whose " Wiirmer" the figure is reproduced 

 (PI. XII, fig. 8). 



3). Kuhn — Description d'un nouveau genre de i'ordre des douves etc. Mem. d. mus. d'hist. 

 nat. T. XVIII, 1829. Also in Anual. d. soien. d'observ., II, 1829. Both cited on the com- 

 bined authority of Diesing, Dujardin, and Brauu. 



4). Nordmann — Mikrographische Beitriige, p. 80. 



5). Thaer — De Polystomo appendiculato, 1851. Also"ireber Polystomum appeudicula- 

 tum " in Midler's Archiv f. Anat. Phys, Jahrg. 1850. The latter is cited on Braun's authority. 



6). P. J. T. Beneden — Memoire sur les vers intestinaux. 1861. p. 54. 



7). Taschenberg— Weitere Beitriige. 



8). P. J. V. Benedsn — Espece noiiTelle de genre Onchocotyle vivant sur les branchies du 

 Scymnus glacialis. Bull. d. I'Acad. roy. d. Belg., t. XX, 1853. p. 59. Cited on the authority of 

 P. J . V. Beneden and Braun. 



