PAPERS ON ZOOLOGY 155 



There are thus representatives of six genera of Acantho- 

 cephala infesting fish of the Illinois River at Havana: 

 Echinorhjnchns, Poniphorhyuchus, Tanaorhamphus, Grac- 

 ilisentis, ]!^eoeehinorhynehns, and Octospinifer. In the 

 region under consideration each of these genera is repre- 

 sented by a single species. The last four of these genera 

 belong to the family Neoechinorhynchidae, which is espe- 

 cially highly differentiated in the North American fauna. 



Of the species of Acanthocephala infesting freshwater 

 fishes of North America but two show strong evidence of 

 restriction to a single host species. TanaorhampJius long- 

 irostris and GraciUscntis graciJiscntis have been recorded 

 from the gizzard shad only. N. cylindratus and 0. maci- 

 lenius, though recorded for a single host species in the 

 accompanying table, are known to occur in other species 

 from other localities. 



It is significant that no larval Acanthocephala were 

 found in any of the vertebrates examined in the region 

 under consideration. 



In the present study four species of Acanthocephala are 

 listed for the first time from the Illinois fauna; Echino- 

 rhynchus thecatiis Linton^ NeocchinorhyncJius cyUndratus 

 (YanCleave), PompJwrliynclius hiilhocolU Linkins Octo- 

 spinifer macilcntns VanCleave. 



Twelve additional fish are added to the host list for E. 

 thccatus, namely: Lcpisosteus platostomiis, Hiodon terggt- 

 sus^ Ictiobus huhaJiis, Carpiodes carpio, Cyprinus carpio, 

 Ictalurus punctatus, Pomoxis annularis, P. sparoides, 

 Lepomis pallidus, Eupomotis gihhosus, Micropterus 

 saJmoides, and Perca flavescens. 



For N. cyUndratus two new host species are reported: 

 Carpiodes carpio and Micropterus dolomieu. 



SUMMARY. 



Over 350 fishes representing twenty-four species from 

 the Illinois river were examined for Acanthocephala, 

 chiefly in the summer of 1910. Of these nineteen species 

 were found to harbor Acanthocephala. 



Six genera of these [)arasites, each represented by a 

 single species, were found in the fishes of the region under 

 consideration. 



