encountered very often among different Monogenoidea. Hence, we can conclude that either 

 Heteronchocotyle does not represent an independent genus but only a stage in the development 

 of some sort of species of Hexabothrildae of typical structure, or else the "formation" of this 

 genus took place by way of reaching maturity during a delay in the one of the stages of post- 

 embryonic development. As is known, such a type of evolutionary development is appraised 

 at the present time as being very progressive and occurring sufficiently frequently in dif- 

 ferent groups. It will be possible to make final conclusions about the independence of 

 Heterochocotyle only after special studies. However, for the time being we consider the 

 preservation of this genus more correct. 



p. 410 



Fig, 292. Heteronchocotyle hypoprioni Brooks, attaching disc of a worm, 

 to Brooks, 1934; B- -Diagram of the supposed structure. 



A- -According 



As regards the remaining 4 genera it is most probable that Squalonchocotyle , 

 in which more simple relations between the vaginal and the vitelline ducts occur, is the 

 most primitive. It is indispensable to note that during the examination of a preserved 

 sample of Callorhynchus antarctlcus Lacepede from Australia obtained in 1884 (collection 

 of Z. L N. Acadecmy of Sciences SSSR, No. 7052) we discovered one damaged specimen 

 of a monogenetic trematode undoubtedly related to Hexabothrildae and apparently to the 

 genus Squalonchotyle. Thus, we can consider that even though they occur very 

 rarely, nevertheless, Hexabothrildae are encountered on Holocephali. 



Until now. In spite of the rather numerous dissections of Chimaera, only representatives 

 of the family Chimaeracolldae have been discovered on them. 



2. Order Chlmaericolidea (Brinkmann, 1952) 

 Bychowsky ord, nov. 



In 1952 Brinkmann isolated the superfamlly Chimaericolidea to which we attribute the 

 status of an Independent order. 



Oligoncholnea, the development of which has not been studied but probably 

 having larvae with 10 edge and 2 to 4 middle (?) hooks. Adult forms of large sizes. Their 

 attaching disc is delimited from the body by a long "stem" devoid of sex ducts and glands. 

 The armature of the disc consists of one pair of edge and 2 pairs of middle hooks and 

 4 pairs of more or less equal clamps each equipped with 3 chitinous parenthesis-shaped 

 sclerites. The cephalic end bears a weakly expressed buccal pseudosucker, 



491 



