13 Acanthocephala collected by the Swedish Expedition 

 to the Juan Fernandez Islands (1916—1917)/ 



By 

 H. J. Van CLEAVE, 



Urbana, Illinois. 

 With Plate 5. 



Through the courtesy of Professor T. Odhner, I have been granted the 

 opportunity of studying the Acanthocephala taken by the Swedish Pacific 

 Expedition (1916 — 17), directed by Dr. C. Skottsberg, to the Juan Fernandez 

 Islands off the coast of Chile. This collection, though relatively small, is of 

 considerable importance because of the extremely meagre data available regard- 

 ing the acanthocephalan fauna of the west coast of South America. Worms 

 of this group occur as parasites in the intestine of all the groups of verte- 

 brates but are frequently overlooked by general collectors. Most of the studies 

 on Acanthocephala from South America have been conducted upon collections 

 from Brazil. The few isolated instances of studies from other localities on the 

 same continent indicate that collections from widely separated localities are 

 fairly sure to contain distinctive species not encountered in other regions. 

 Previous studies have demonstrated that many species af Acanthocephala are 

 sharply limited in the extent of their geographical distribution. No lists are 

 available that would make possible a comparison of the species collected by 

 the Expedition and those that might be encountered on the nearest mainland. 



In the collections secured by the Expedition but three species of Acan- 

 thocephala are represented. Two of these are from the intestine of fishes and 

 the third from the intestine of a gull. The fish parasites include a new species 

 of the genus Rhadinorhynchus and another new species for which it has been 

 necessary to erect a new genus, Tegorhynchis for which T. brevis is designated 

 as type. 



A single specimen of the genus Arhythmorhynchus from Lams domini- 

 camis belongs to a previously unrecognized species which is here described as 

 Arh. teres. 



' Contributions from the Zoological Laboratory of the University of Illinois, No. 173. 



