Dactylogyridae .having an attaching apparatus with 14 edge 

 and 2 nniddle hooks; the latter are sometinnes absent. The connecting 

 and supplementary plates usually exist, less often the second is 



absent; among fornns without middle hooks there is no connecting 

 apparatus. The intestinal trunks lack lateral outgrowths, they 



merge at the posterior end. The testis is single; the vaginal duct, for 

 the most part, is at the side of the body, less often on the ventral 



side, still less often is absent. 



Parasites of freshwater and marine Teleostei. The vast 

 majority of species occurs on Cypriniformes. 



Type genus, Dactylogyrus Diesing, 1850. 



Five other genera pertain hereto: Dogielius Bychowsky, 

 1936, Falciunguis Aronerow, 195Z, Pseudacolpentron Bychowsky and 

 Gussew, 1955, Acolpenteron Fischthal and Allison, 1940, and Para - 

 dactylogyrus Thapar, 1948. 



Regarding the first two genera there are no doubts that they 

 are derivatives of Dactylogyrus and are very close to it. Likewise, as 

 we show in our common work with Gussew (Bychowsky and Gussew, 1955), 

 without any doubt the genus Pseudacolpenteron originates either from 

 representatives of the genus Dactylogyrus o r from ancestors common 

 with the latter, and in such a fashion one can consider itsinclusion into 

 the given subfamily as legitimate. The situation of Acolpenteron is more 

 complex. One can hardly doubt that A. nephriticum Gvosdev descends 

 from some sort of species of Dactylogyrus or fronn forms close to the 

 present genus; whereas, it is impossible to say anything certain about 

 the two remaining species- -A. ureterocoetes Fischthal and Allison and 

 A. catostomi Fischthal and Allison. If one can suppose that the second 

 species descends from sonne sort of Dactylogyrinae or Ancyrocephalinae 

 with an equal degree of probability, the first, on the other hand more 

 probably originates from some sort of Ancyrocephalinae, because only 

 the representatives of the last subfamily are known on Centrarchidae 

 (hosts of the present species). It is very improbable to expect that 

 A. ureterocoetes stems from some sort of Dactylogyrinae and that it 

 switched from parasitizing Cypriniformes (for instance Catostomidae) 

 to Centrarchidae. As we have already indicated with A. V. Gussew, 

 this species, as all other representatives of Acolpenteron and 

 Pseudacolpenteron are forms which were secondarily simplified in 

 connection with the utilization of the new place of habitat on the same 

 species of host (topological origin of conjugate species -genera, 

 according to the terminology of V. A. Dogiel, 1949). Hence, one must 

 recognize it as more probable that the genus Acolpenteron in its present 



411 



