TWO NEW GENERA AND SPECIES OF ACANTHOCEPH- 

 ALOUS WOKMS FROM VENEZUELAN FISHES. 



By H. J. Van Cleave, 



Of the University of Illinois, Urbana, Illinois. 



With the exception of the species parasitic in birds and in mam- 

 mals, practically nothing is known of the acanthocephalan fauna 

 of South America. K. M. Diesing (1851) described a number of 

 species of these parasites from the Brazilian collections by Natterer 

 and by Olfers which included a few species from fishes. These 

 were briefly characterized by the enumeration of a few salient fea- 

 tures of external morphology. The drawings accompanying these 

 descriptions are so highly generalized that they add but little to 

 the data available for the recognition of Diesing's species. In spite 

 of the fact that his records indicate some interesting deviations from 

 the conditions and structures found in the better known European and 

 North American species, no one has yet made a successful attempt 

 to include his forms from fishes in the modern system of classifica- 

 tion which, for this group, has been evolved in the last quarter 

 century. 



No recent worker has published an account of having restudied 

 or even of having recognized any of Diesing's species of Acantho- 

 cephala from Brazilian fishes. In fact, there is no published record 

 including results of a careful study of the Acanthocephala from 

 fresh-water fishes of any locality on the South American continent. 

 Porta (1905) in his general catalogue of the Acanthocephala of 

 fishes listed Diesing's species, but with no data beyond that included 

 in the original descriptions. Recently a considerable body of evi- 

 dence has been accumulating (Van Cleave 1916 a: 228, 1918:20 and 

 32, 1919:234) emphasizing the distinctive features of the North 

 American acanthocephalan fauna as contrasted with the European 

 fauna, upon which the modern system of classification of the group 

 has been chiefly based. It is not improbable that the incompletely 

 described and imperfectly known novelties in Diesing's work may 

 represent another line of independent diiferentiation characteristic 

 of the Acanthocephala of the South American continent. Phylo- 

 genetically the Acanthocephala represent such an ancient group of 



Proceedings U. S. National Museum, Vol, 58-No, 2346. 



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