126 ILLINOIS BIOLOGICAL MONOGRAPHS [126 



seems to be no exception. That Nufer made a misdetermination of his 

 P. longicollis is not at all improbable since specimens labelled ^'Taenia 

 longicollis aus Forelle" which have been received by Professor Ward 

 from Professor Zschokke have proved to belong to a different species. 

 Nufer 's tabulated description of P. longicollis (Nufer 1905:147) does 

 not agree in some important points with von Linstow's description yet 

 it is very manifest that he drew on von Linstow's description for a 

 large part of his data. Likewise parts of Nufer 's description of P. 

 torulosus (Nufer 1905:147) fail to agree with the descriptions of that 

 species by Schneider and Kraemer. Liihe (1909:32) gave a short spe- 

 cific description of this form under the name of Ichthyotaenia torulosa 

 (Batsch). La Rue (1911:475) listed this form among other species of 

 Proteocephalus. 



The following study is based upon some of Schneider's specimens 

 which Prof. H. B. Ward secured from Professor Levander at Helsing- 

 fors. This material is labelled ^^Ichthyotaenia torulosa Batsch. Leucis- 

 cus idus. Porkala. Juni 1901. det. G. Schneider." It now bears the 

 number 10.121 in Professor Ward's collection. From this material 

 frontal and transverse sections have been made and some heads have 

 been studied in glycerine. A careful comparison of Schneider's (1905) 

 and Kraemer 's (1892) descriptions shows very good agreement. Zschok- 

 ke 's (1884) description in parts agrees pretty well with these two. Liihe 

 (1909) seems to have based his specific description largely on the work 

 of Zschokke, Kramer, and Schneider. Data from these sources are used 

 in this description. 



This is one of the larger species of Proteocephalus infesting fish. 

 In length it varies from 65 to 600 mm. Specimens of the latter length 

 are rare and have been reported only by some of the earlier investigators. 

 The longest complete strobila examined by the writer was 110 mm. long. 

 The breadth of the strobila varies from 1.2-2.25 mm. The head (Fig. 7) 

 is large and very prominent, somewhat swollen in appearance, flattened 

 dorso-ventrally, and somewhat flattened at the apex. Schneider found 

 it 0.500 mm. broad. The heads in the writer's material measured 0.450- 

 0.600 mm. broad by about 0.320 mm. thick. The suckers are very prom- 

 inent, nearly circular in outline, with deep cavities and strong muscu- 

 lature. They are directed anteriad and a little outward. The suckers 

 are 0.200 mm. in diameter according to Schneider and about 0.180-0.200 

 mm. in the heads examined by me. A fifth sucker is not present. In 

 sections of the head the writer was unable to find even a trace of a 

 vestigial fifth sucker. Nufer (1905:147) stated that the head of a 37 

 mm. specimen measured 0.255 mm. broad and the suckers of the same 

 were 0.10 mm. in diameter. Nufer 's measurements of the head do not 



