Hypophthalmichthys (Gussew, 1955). All the five species on which D. 



magnichamatus was found by Gussew belong to one subfannily--Cultrinae 



and thus are related in a certain degree to each other, whereas 



which Achmerov described this species belongs to the subfamily of 



Hypophthalmichthyinae, generally distant from Cultrinae. It is difficult to 



say anything definite until new studies, but it seenns to us that the data of p. 241 



Achmerov demand very thorough verification. It is possible that here there 



was some error in labeling. All in all this is the only case from the genus 



Dactylogyrus which does not fit into the "rule of Bychowsky. " 



Among the species of other genera of Monogenoidea related to 

 the groups encountered on two or more genera related to one family of 

 fishes,, an overwhelming majority is discovered in representatives of more or 

 less closely related genera. Among the species of this group a few cause 

 perplexity and because of that we must deal primarily with them and also 

 with several others which deserve attention for different reasons. First 

 of all one must discuss the occurrence of certain representatives of the 

 genus Diclidophora. Thus,D, denticulata OUson and D. maccallumi (Price) 

 are indicated as discovered on Gadidae belonging to different subfamilies 

 and D. poUachii (Beneden and Hesse), D. minor (Ollson) and D. morhuae 

 (Beneden and Hesse) which are on genera that are quite distant from each 

 other even though they are of one subfamily. During more careful re- 

 examination it appears, however, that all these worms apparently occur 

 each only on one species of hosts and the indications (that they occur, 

 nobis) on the others are faulty or erroneous. 



Thus, D. denticulata is indicated from Merluccius merluccius 

 (L. ) on the basis of the data of Baylis and Jones (Baylis and Jones, 1933) 

 who found this species on the given fish in Plymouth. However, as 

 Sproston quite correctly notes (Sproston, 1946) these data are based on 

 an erroneous determination of the host "because of the superficial 

 similarity of M. merluccius to Gadus ( = Pollachius) virens--a mistake often 

 made by non-ichthyologists. " This is substantiated by the fact that in 

 the region of Plymouth, D. denticulata is very common on the Pollack, 

 whereas it has never since been discovered by anyone on M. merluccius . 



The case of the finding of D. denticulata on Trisopterus 

 minutus (Miill. ) is not clear--there is only one indication of Parona 

 (Parona, 1899, 1902) about the given host. Probably there is some mis- 

 take. Thus the authentic host of D. denticulata is only one species -- 

 PoUachius virens (L. ) on which this worm is encountered rather frequently 

 practically throughout its entire range. 



D. maccallumi was described in Price (Price, 1943a) only 

 from one species, Urophycus chuss (Wall. ); whereas the indication of its 

 finding on Merluccius bilineatus (Mitch. ) which was not taken into consider- 

 ation by Price and cited anew, completely uselessly, by Sproston in her 



269 



