1. Two genera--Pseudaxine and Haliotrema --are encountered 

 on five families of fishes. Both genera infect representatives of one order 

 and predominantly are encountered in a closely related group of families. 

 At the same time. the basic mass of species of Haliotrema is discovered 

 on one family of hosts. 



2. Correspondingly, on four families of fishes we encountered 

 four genera- -Diplectanum, Heteraxine, Trochopus , and Entobdella , The 

 first two genera are found on relatively close families, Trochopus - -mainly 

 on two closer and more seldom on two more remote fannilies, and finally 

 Entobdella on three families related to each other and on one not related 

 with the preceding ones. 



3. On three families of fishes are encountered three mono- 

 genetic trematodes--Axine, Octostoma and Megalocotyle ; in all three cases 

 representatives of the genus are encountered on two consanguinously related 

 families and one family which does not have any close genetic links; the 

 representatives of one of these genera ( Axine ), in the basic mass of species, 

 parasitizes both families of related fishes and only one species is encountered 

 on the third. 



4. Finally, the genus Cleidodiscus should be considered as 

 artificial; however, it is noted that basically it is encountered on one 

 family of fishes and only in a small number of species on three other 

 families not related to the first. 



Three genera- -Calicotyle, Squalonchocotyle , and Urocleidus 

 are each indicated on seven families of fishes (Table 13). The first of 

 these genera is undoubtedly located on seven families; namely, on three 

 families of sharks, three--skates and on chimaeras. The data about the 

 finding on Bothidae, "of which we spoke earlier, are discarded by us (see 

 page 227 ). One should indicate that there are no species occurring only 

 on chimaeras; however, there is one species C. affinis Scott which is 

 known predominately on them and Raja fuUonica. The consanguinous 

 relations of the sharks and skates are sufficiently known. As regards 

 their links with Chimaera they are, as is understandable, more distant. 



The genus Squalonchocotyle is discovered indisputably on six 

 families and basically on five families of sharks related to each other in 

 the wide sense and on one family of skates. The indication of the finding 

 of Squalonchocotyle on Serranidae refers to S. mavori , described by Linton 

 (Linton, 1940), and actually is based on a nni sunder standing as was indicated 

 on page 228 . All in all, one nnust consider that only six families of Selachii p. 261 

 are hosts of Squalonchocotyle. 



294 



