The genus Urocleidus, just as Cleidodiscus, should be ex- 

 cluded for the time being from the discussion as being artificial, noting 

 however, that it is basically encountered on perciformids, mainly on Centrarchidae. 



Two genera are encountered on eight families of fishes each-- 

 these are Capsala and Tristoma (Table IZ). Both genera are too complex 

 to be discussed because of the very intricate synonymies and, in this 

 connection, because of the very contradictory data about their occurrence. 



The genus Capsala is authentically known from seven families, 

 and data of its finding on Squalidae should be considered erroneous. They 

 are cited in the work of Blanchard (Blanchard, 1847) who found a worm once 

 on Squalus sp. in New Zealand which he described under the name of 

 Tristoma squali. The attribution of this species to the genus Capsala (Price 

 1938b, 1939 and others) seems to us incorrect. It should rather be con- 

 sidered as a representative of the genus Tristoma . As a basis for this 

 serves the drawing from "Le Regne Animal" Cuvier (edition under the 

 editorship of Blanchard and others), where T. squali is drawn on Table 36 

 (Figures 2 and 3, a) with the following text: This is translated by us from 

 the French "This species was taken from the gills of Squalus from New 

 Zealand by Mr. Jules Verraux. " These drawings show that the species 

 which interests us is equipped with thorns along the edge of the body which 

 are well-developed among representatives of Tristonna and Capsaloides, but 

 which are absent or weakly developed among Capsala . Seven families of 

 the actual hosts of Capsala are divided into two groups which have no direct 

 consanguinous links with each other. To the first belong five families 

 (Cybiidae, Histiophoridae, Xiphiidae, Thunnidae, and Coryphaenidae) which, 

 according to Gregory, unite as Sconnbroidei and to the second--Molidae and 

 Diodontidae; as a matter of fact, in the last family there is no independent 

 species of Capsala, and it is possible that this indication is erroneous. 



Without any doubt, the genus Tristoma is encountered on three 

 families of Scombroidei (according to Gregory), that is on Xiphiidae, 

 Histiophoridae and Thunnidae. One can strongly doubt the correctness of 

 the data about the finding of Tristoma on the remaining five families of 

 fishes. Thus, Tr. uncinatum Monticelli is indicated for Pleuronectidae. 

 This worm is reported on Pleuronectes sp. (?) on the basis of preparations 

 of Leuckart on whose labels there are no data about the location of its 

 finding (Monticelli, 1889). Because this species has not been encountered 

 by anyone else until now, one can suppose that there is here a certain error. 

 The indications of the finding of Tristoma on Molidae are obviously erroneous. 

 The finding of Tr. coccineum on Mola mola according to Price (Price, 1939) 

 is doubtful, and it is possible that the indication to the discovery of' Tr. 

 papillosum is based on an error of determination (Sproston, 1946). Tr. 

 fxihrmanni Guiart is indicated for Rajidae. Actually this Species is not 



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