13. Acanthocephala collected by the Swedish Expedition 
to the Juan Fernandez Islands (1916—1917).' 
By 
He Ee VaAn CEA E. 
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, 7egorhynchus for which 7. brevis is designated 
as type. 
A single specimen of the genus Arhythmorhynchus from Larus domint- 
canus belongs to a previously unrecognized species which is here described as 
Arh. teres. 
1 Contributions from the Zoological Laboratory of the University of Illinois, No. 173. 
