What has been indicated seems to us fully sxifficient to consider 

 the separation of the given group into a special family as correct or in 

 order. Its isolation undoubtedly is linked in the historical aspect with a 

 change fronn parasitizing marine fishes to living on fresh water fishes. 



The attaching clamps of Discocotylidae (Fig. 300) are arranged p. 425 

 somewhat simpler than among the preceding families of this order. They 

 have muscular walls in which 5 chitinous plates (sclerites of other workers, 

 nobis) are located. The first of them lies in the medial 



line across both valves in such a fashion that its larger part is located in 

 the anterior valve. This plate corresponds and is homologous to the basal 

 plate of Plectanocotylidae (see page 429 ) and usually has ends which are of 

 characteristic shape for separate species, to which the corresponding 

 muscular clusters are attached. Along the lateral edges of the anterior 

 valve lie the 2 plates, which are mirrored in relation to each other, with 

 their anterior ends drawn close to each other and to the anterior end of the 

 middle plate. The posterior parts of these plates extend beyond the limits 

 of the anterior ones and are located in the posterior valves in such a fashion 

 that their ends are oriented toward the posterior end of the middle plate. 

 On the whole, there are the three elements which fornn the spring system of 

 the clamp. At the place of the transition of the lateral plates into the 

 posterior valve, toeach of which is articulated a frail plate which proceeds 

 along the edge of the posterior valve toward the middle where they very 

 often adjoin very closely against each other. Frequently these plates are 

 connected together by a special tendon (compare with the posterior "lip" 

 of Plectanocotyle !- -page 429 ). As a w^hole,the clamps of Discocotylidae 

 have, as is apparent from the description, mirrored right and left halves 

 and a different structure of the anterior and posterior valves. With this, 

 one must bear in inind that the posterior valve is less mobile than the 

 anterior, which is connected with the nature of its location in relation to 

 the body of the animal. It is connected to it by its large surface, whereas 

 the anterior valve is more free. Let us note also that we can speak with 

 a high degree of probability about the homology of the lateral plates of the 

 anterior valve with the parentheses of Chimaericolidae and the corresponding 

 plates of Plectanocotylidae, whereas the plates of the posterior valve can 

 be subjected to homologization only with great difficulty. However, as will 

 be seen from that which follows (see page 429), they are most probably 

 homologous to the lip and the lateral plates of the posterior valve of the 

 clamp of Plectanocotylidae and also to the lip of the posterior valve of 

 Mazocraeidae. 



1. Subfamily Discocotylinae Price, 1936 

 (Figs. 228-230, 300) 



509 



