scope, is artificial and its attribution to Dactylogyrinae can be considered 

 as conditional. 



One more question arises, is it correct to include the forms 

 in which middle hooks are absent, the number of which, as we have 

 seen earlier represents a very significant peculiarity into the circle of 

 Dactylogyrinae? In other w^ords, would it not be more correct to 

 isolate these forms into a special subfannily? Generally speaking, we 

 attribute great systematic significance to the absence or presence of 

 middle hooks and also to the number of pairs of the latter, and if their 

 absence among Acolpenteron and Pseudacolpen teron were primary we 

 would not have doubted the correctness of the placement of these genera p. 348 

 into a special subfamily. But since the absence of middle hooks among 

 both genera is a secondary phenomenon,we do not consider it possible 

 to accept this peculiarity as essential in the present case because the 

 difference between the initial and the ones derived from them do not have 

 the nature of new formations which could be used to characterize a new 

 large systematic group. 



As regards the genus Paradactylogy r us , its independence is 

 very doubtful and it is more likely that the only species of this genus 

 nnust be included in the genus Dactylogyrus. 



2. Subfamily Ancyrocephalinae Bychowsky, 1937 



(Figs. 10, B, 13, 46, 55, A, 65, 79, 92, 101, B and C, 106, 

 113, D, 118, 121, 151-180, 266. 267) 



Tetraonchinae Monticelli, 1903, part . 



Dactylogyridae, having an attaching apparatus with 14 edge, 

 4 middle hooks and connecting plates numbering 2-4 which are some- 

 times absent. The intestinal trunks are without lateral outgrowths with 

 the exception of Tetrancistrum Goto and Kikuchi which has outgrowths. 

 The intestinal trunks terminate blindly or merge at the posterior end. 

 The testis is single. For the most part, the vaginal tract is on the 

 ventral side, less often on the side of the body, often is absent. 



Parasites of fresh water and marine Teleostei. The vast 

 majority of species is on Perciformes. 



Type genus, Ancyrocephalus Creplin, 1839. 



In addition to the type genus, 25 genera belong here: 



412 



