298 ILLINOIS BIOLOGICAL MONOGRAPHS [298 



Proteocephalus pinguis 



P. pinguis is a North American species found in widely separated 

 localities. It has been found in small lakes of Maine, Michigan and 

 Wisconsin, It has not yet been found in the Great Lakes. Further 

 collections may show a much wider distribution for this species. The 

 hosts, Esox lucius and E. reticulatus, have a wide distribution. Esox 

 lucius is a cosmopolitan species of the northern hemisphere, occurring 

 in the fresh waters of Europe, Asia and North America. In North 

 America its range is from Alaska south to the upper Mississippi valley, 

 east of the Rockies to the Potomac. Esox reticulatus is common east 

 and south of the Alleghanies to Louisiana, and Arkansas. The ranges 

 of these hosts are common east of the Alleghanies to the Potomac river. 



Both hosts are voracious carnivores, eating fish, frogs, crawfish, 

 mice, reptiles, water birds, and larger insects. That these two host spe- 

 cies harbor the same species of Proteocephalus is then not remarkable. 

 Since, however, Esox lucius is common to Europe and North America 

 one might expect to find it harboring the same species of Protecephalus 

 in both continents. Such does not seem to be the case. This fact sug- 

 gests that these two species, P. pinguis from North America and P. 

 esocis found in the European Esox, have arisen as varieties of the same 

 species or that the host upon going into the new region, either Europe 

 or North America, has acquired a new species of parasite. 



Proteocephalus pusUlus 



This species occurs in Sebago Lake, Maine, and Lake Temagami 

 Ontario. Its hosts are Salmo sehago and Cristivomer namaycush. 

 These two salmonids live ou^y in fresh water and their habitats overlap 

 to a certain extent. Salmo sehago, according to Jordan and Evermann 

 (1896), occurs in Sebago Lake and northward, in lakes, rarely entering 

 streams. Cristivomer namaycush lives in the lakes of New York, New 

 Hampshire and Maine and westward to the headwaters of the Columbia 

 and north to the Arctic circle (Forbes and Richardson, 1909). Both 

 fish are predaceous, living largely on fish. Professor "Ward's records 

 show that in Sebago Lake Salmo sehago was feeding on Osmerus mor- 

 dax. Records are too meager to allow the making of any general 

 conclusions. 



Proteocephalus sulcatus 



This species is known only from the Nile River, from two widely 

 separated hosts, namely Polypterus endlicheri and Clarotes laticeps. 

 The former is one of the Polypteridae, a Crossopterygian, while the 

 latter named host is a Silurid, of the order Teleostei. Both hosts occur 

 in the Nile. The food habits of Polypterus endlicheri are not well 

 known. One species of Polypterus feeds on small teleosts while others 



