-296 ILLINOIS BIOLOGICAL MONOGRAPHS [296 



Proteocephalus macrocephalus 

 This species has the widest distribution of any known Proteocepha- 

 lid. It has been taken in many localities of northern, central and south- 

 ern Europe and from two localities in eastern North America. Its hosts 

 are Anguilla vulgaris and A. chrysypa. The former has a wide range 

 over most of Europe, north Africa and temperate Asia. It is lacking 

 in the Black and Caspian Seas. By some authorities this species is 

 thought to be found also in North America. Others, including Jordan 

 and Evermann (1896-1900) make the American form a separate species, 

 calling it A. chrysypa. This species occurs over the most of North 

 America east of the Rocky Mountains, including Mexico and the West 

 Indies. The food habits of the two species are alike. They are vora- 

 cious, and act as scavengers, preferring dead fish or other animal refuse. 

 In view of their close relations and their similar habits it is not surpris- 

 ing that these species harbor the same species of parasite. 



Proteocephalus percae 

 The geographical distribution of this species is imperfectly known. 

 Up to the present time it has been taken only in East Prussia, Finland 

 and Sweden. It has not yet been reported from the Swiss lakes tho 

 two of its host species are abundant in that region. These hosts are 

 Perca fluviatilis and Coregonus maraena (fera). The appended table 

 •gives the data as to hosts, their distribution and food habits. An exam- 

 ination of the table shows certain points of interest. Perca marina 

 which Miiller gave as a host of this parasite is little known, nor is Perca 

 norvegica which Rudolphi said was the host of Miiller 's parasite. The 

 .remaining host species overlap in their distribution. Likewise their 

 food habits overlap to a certain extent. All eat bottom fauna tho Perca 

 fluviatilis preys more on other fishes than do the other hosts. The food 

 habits of P. fluviatilis and Coregonus maraena show close resemblance. 

 These two species are known to harbor the species which Schneider 

 (1905) describes as Ichthyotaenia percae (Miiller). Acerina cernua 

 and Gasterosteus aculeatus may harbor this parasite but it seems doubt- 

 ful. These two species are known to harbor Proteocephalus cernuae 

 and P. filicollis respectively. It seems that there may have been a mis- 

 determination. The parasites of these two hosts and of Cottus quadri- 

 cornis should be subjected to a re-examination. 



