is deprived of chitinous armature. Let us also note that in the time which 

 followed the publication of our work, P. pacificunn Bychowsky and Gussew 

 ■was discovered several times by us on its host from different regions from 

 the Sea of Okhotsk. 



As regards the justification of the separation of Diclybothriidae 

 into an independent family, as we succeeded in showing with Gussew, the 

 differences between this family and Hexabothriidae into which they were 

 included are very important. Thus, although the attaching disc has a 

 principal similarity in both families, the degree of the divergence between 

 Diclybothrium and Paradiclybothrium on the one hand, and Hexabothriidae 

 s. str. on the other--is very significant. As is apparent fronn the corre- 

 sponding diagnoses, the structure of the anterior end in both families is 

 different. There are also differences in the structure of the digestive and 

 sex systems, although they are less important. Finally, the adult forms 

 and probably also the larvae of both groups sharply differ by the presence 

 of 4 eyes in Diclybothriidae and their complete absence in Hexabothriidae. 

 Nevertheless, all this, as well as the parasitizing of different groups of 

 hosts, which also confirms the importance of the divergence of both 

 families, appears quite sufficient for the separation of the Diclybothriidae 

 into an independent family. 



2. Family Hexabothriidae Price, 1942 



(Figs. 2, 36, 67, 101, I, N, 290-292) 



Onchocotylinae Monticelli, 1903; Onchocotylidae Stiles and 

 Hassal, 1908. 



Diclybothriidea, having middle and large sizes in the adult 

 stage. The attaching disc is subdivided into two parts --the anterior widened 

 and the posterior narrowed, and having the shape of a more or less narrowed, 

 mobile offshoot. The anterior part of the disc bears 6 clamp-shaped suckers, 

 each equipped with a powerfully developed edge hook. The posterior part 

 of the disc is equipped with 2 small muscular and relatively deep suckers 

 and 2 middle hooks lying along the posterior edge of the disc between the 

 suckers. In sc;parate cases the middle hooks can be absent (?). The p. 406 



anterior end has a nnore or less strongly developed preoral sucker. The 

 eyes are absent. The intestine is two-branched with weakly branching 

 lateral and middle outgrowths. The branches of the intestine merge at 

 the posterior end of the body and form more or less well-developed ranai- 

 fications in the disc, from which one extends into the narrowed part of the disc. 

 The copulatory organ is equipped with chitinous hooks or more often is 

 deprived of arnnature. The testes are numerous. The ovary is pipe-shaped, 

 wavy, in froiit of the testes. The vaginal ducts are paired and open as a 

 rule by 2 lateral apertures. 



486 



