8o 



Roosevelt Wild Life Bulletin 



In a recent paper (Van Cleave, '20) the writer l]as outlined the 

 trend of development of this species. Larvae of E. thecatus have 

 been found undergoing their development in the amphipod crustacean 

 Hyalella knickerbockeri. Evidence already cited in this paper seems 

 to prove that infestation of the definitive host may occur directly 

 through this primary host. On the other hand, encysted larvae of 

 this species have been taken from the mesenteries of Perca Uave- 

 scens, Micropterus salmoides, Ambloplites rupestris, and Percina 

 caprodes, thus demonstrating that these species may serve as inter- 

 mediate hosts of E. thecatus. Since Hyalella is included in the fauna 

 of Oneida Lake, it is entirely probable that it serves as primary host 

 of E. thecatus though no actual demonstration of this fact is at hand. 



Neoechinorhynchus cylindratus (Van Cleave, 1913). 



Body large, almost cylindrical, except in young forms, in which 

 the posterior extremity is gradually narrowed. Females 10 to 15 mm. 

 long, with a maximum diameter of 0.7 mm. Males 4.5 to 8.5 mm. 

 long and 0.5 to 0.7 in diameter. Proboscis slightly broader than 

 long (0.172 by 0.150 mm.). Proboscis hooks arranged in three 

 circles of six hooks each. Embryos within gravid female 49 to 51/^ 

 long by 15 to 2i/>i broad. 



Neoechinorhynchus cylindratus is the only representative of the 

 family Neoechinorhynchidae encountered in the collections from 

 Oneida Lake. Five of the nine species of fish carrying Acantho- 

 cephala harbored this species. As hosts for this species, Esox 

 reticulatus and Stizostedion vitreum are made a matter of record 

 for the first time. The writer has encountered A'^. cylindratus in 

 the pike-perch from the upper Mississippi River, and from Lake 

 Erie at Sandusky, Ohio, but there is no previously published record 

 of the occurrence in this host. 



Table IL 

 Analysis of the occurrence of A^. cylindratus in Oneida Lake hosts 



HOST SPECIES 



Number 

 infested 



with 

 Acantho- 

 cephala 



Vial numbers 



Number 

 infested 

 with N. 

 cylin- 

 dratus 



Speci- 

 mens in 

 individual 

 hosts 



Slizosiedion vitreum . . 

 Micropterus dolomieu. 

 Micropterus salmoides 



Esox reticulatus 



Anguilla rostrata .... 



72, 74. 75, 182, 183 



120 



99 



I2S 



From the above table it is obvious that Stizostedion vitreum is the 

 most generally utilized host oi N. cylindratus in Oneida Lake. The 

 six specimens taken from one individual of A. rostrata were all 



