NEW GYRODACTYLOID TREMATODES FROM AUSTRALIAN FISHES. 



TOGETHER WITH A RECLASSIFICATION OF THE SUPER-FAMILY 



GYRODACTYLOIDEA. 



By Professor T. Harvey Johnston, M.A., D.Sc, and 0. W. Tiegs, M.Sc, 

 Walter and Eliza Hall Fellow in Economic Biology, University, BrisbanJe. 



(Plates ix.-xxii., and one Text-fig:iu'e.) 



[Read 26th April, 1922.] 



Australian Trematodes have received considerable attention from certain 

 parasitologists, among whom are to be mentioned especially S. J. Johnston and 

 W. Nicoll. These authors, however, have confined their attention almost en- 

 tirely to digenetie species. Of the monogenetic forms no Gyrodactylid has so 

 far been recorded from Australia; indeed, only two species have been described 

 from the Southern Hemisphere, viz. Fridericianella ovicola Brandes and Lopho- 

 cotyle cyclophora Braun from South America. A considerable number of forms 

 are known from central Eui-ope, mainly as a result of the work of van Beneden 

 and Hesse, Wagoner, Perugia and Parona, Diesing, Creplin, Wegener and a few 

 others. A number of species have been discovered in North America, most of 

 them by MacCallum, while Goto has recorded a few from Jap'an. 



In the present paper seventeen new species are described, all from the gills 

 of Australian marine and freshwater fishes. As was to be expected, these were 

 found, with two exceptions, to be generically quite distinct from any hitherto 

 described. Some have proved to be so remarkable that they must fall into a 

 new family {Protogyrodactylklae) , whilst others cannot be included in any of the 

 other known subfamilies, as defined by various authoi-s. This has made possible 

 a considerable extension of our conception of this group of Heterocotylean Tre- 

 matodes and the opportunity has been taken to suggest a reclassification of the 

 gi'oup and to incorporate, and to a certain extent rename, some remarkable 

 species described by MacCallum from North America. This matter has been 

 rendered very difficult by the imperfect accounts of some of the forms; indeed, 

 so many essential characters have been omitted from these descriptions, that 

 it has been found necessary, occasionally, merely to append certain genera to 

 certain subfamilies or families from which they may have to be removed when 

 our knowledge of them is more complete. 



With the exception of two new species, one assigned to Monocotyle and the 

 other to Calaeostoma, all the new Australian forms described in this paper fall 

 into new genera; indeed most of the species considered are so distinct from one 

 another that they have had to be regarded as new generic types. Since only 

 a relatively small number of host-species was examined for the presence of 

 these trematodes, and as the parasites were often present on the gills, especially 

 in the freshwater forms, in enormous numbers (sometimes as many as a dozen 

 on a single minute g-ill-filament), it seems that this gi'oup, if more extensively 



