supplementary chitinous parts which serve for the strengthening of the disc 

 and the attachment of the musculature and which enter into the system 

 of armature, but which do not bear by themselves the function of attach- 

 ment. The cephalic end is equipped with paired clusters of efferent 

 ducts of the cephalic glands; it is flattened and forms 1-3 pairs of 

 short tentacle -shaped growths. In the nnajority of the cases there are 

 2 pairs of eyes, more seldom one pair; sometimes the eyes can be 

 secondarily absent. The intestinal branches merge at the end or 

 terminate blindly. The ovary is rounded and, more seldom, flask-shaped; 

 the vaginal duct, if it exists, is single; the vitellaria are strongly 

 developed, they are paired; there is only an obtype containing one egg 

 at a tinne, with the exception of the genus Linguadactyla Brinkmann 

 which has a true uterus. The copulatory. organ is chitinous*, for the 

 nnost part its pipe is supported by one or several chitinous parts con- 

 nected with each other and with the pipe, more seldom the connections 

 are absent. The male sex orifice is on the ventral side of the body, for 

 the most part medially. 



Parasites of fresh water and marine Teleostei, predomi- 

 nantly Cypriniformes and Perciformes. 



In spite of the fact that almost one -half of the known mono- 

 genetic trematodes belong to this family its system has been very poorly 

 studied. One must suppose that this is a result of two circumstances; 

 on the one hand, because of the unusual variety of separate chitinous structures, 

 on the basis of which not only species but also the genera are separated; 

 on the other hand, because of the relatively small sizes of the worms, as 

 a result of which the study of their interior structure is considerably 

 impeded. In the present work we do not consider it our problem to 

 analyze this family more in detail, limiting ourselves only to the establish- 

 ment of basic tendencies of its development and hence to the subdivision 

 into subfamilies and groups within the limits of the latter. 



The family includes three subfamilies: Dactylogyrinae 

 Bychowsky, Ancyrocephalinae Bychowsky and Linguadactylinae Bychowsky 

 subfam. nov. 



1. Subfamily Dactylogyrinae Bychowsky, 1933 p. 347 



(Figs. 3, 5, 32, A-C, 33, A-H, 44, 45, 96, 101, A, 108, 111, 

 119, 120, 132, 134-150, 261, 311, 312, A, B) 



Gyrodactylinae Monticelli, 1892, part. 



410 



