A canthocephala 



5e 



A comparison of F. arcticus with other known members of the same genus 

 discloses some interesting facts regarding the geographical distribution of the 

 members of this genus. F. anatis is the common European representative of 

 Filicollis while F. botulus occurs in the Eiders in the United States. Filicollis 

 arcticus, n. sp., differs in definite manner from both the previously mentioned 

 species but shows a distinctly closer relationship to F. botulus. Embryos 

 within the body cavity of the gravid female of the last named species range 

 from 71 to 83 fi in length while those of F. arcticus vary from 126 to 155 fx. The 

 two American species also differ in the number of hooks on the proboscis. In 

 F. botulus there are but sixteen longitudinal rows of hooks while for F. arcticus 

 the writer has found twenty-two. Both of these American species lack the 

 spherical enlargement of the proboscis characteristic of the European species. 



The King Eider, the host of F. arcticus, though circumpolar in its distri- 

 bution, evidently does not carry the same acanthocephalan infestation through- 

 out its range. From the West Tajmirland peninsula, von Linstow (1905:3) 

 described Echinorhynchus pupa from this same host species. Unfortunately 

 his description and his figures of this species fail to give a full enough account 

 of the structure to enable anyone to place it with certainty in any of the genera 

 recognized in modern taxonomy of the Acanthocephala. In his figure of a 

 peculiarly coiled specimen the first loop posterior to the proboscis fails to show 

 any connection with the rest of the body. No mention is made in the text of 

 any peculiarity in the structure of the neck or anterior body region so it seems 

 probable this is not a unique structure but is simply an error in the execution 

 of the drawing. No evidence is presented, either in his description or in his 

 figures, which would make it seem probable that his species belongs to the 

 genus Filicollis. Thus on opposite sides of the arctic circle the King Eider 

 apparently is parasitized by Acanthocephala representing two distinct genera. 



Echinorhynchus salveUni Linkins, 1918 (In Ward and Whipple). 

 (Plate II, Figs. 6 to 9). 



Color : orange or greenish yellow ( Johansen's notes) . 



Specific Diagnosis. — With the characters of the genus. Anterior portion 

 of body-proper rather conspicuously enlarged, especially in the females. Males 

 7 to 12 mm. long and 0-8 to 2 mm. in maximum diameter. Females 10 to 20 

 mm. long and 1-2 to 2-25 mm. in maximum diameter. Proboscis cylindrical, 

 armed with sixteen to eighteen longitudinal rows of about thirteen hooks each. 

 Basal hooks about 39 to 50 fi long, hooks on middle and anterior regions of 

 proboscis 44 to 68 n long, some with a root about 83 ij. long. Lemnisci short, 

 little longer than proboscis receptacle. Embryos within body cavity of gravid 

 female 115 to 165 /x long by 20 to 25 fi broad, middle membrane forming a pro- 

 longation at each pole more than twice as long as it is broad, frequently charac- 

 teristically curved. 



Arctic hosts: Cristivomer namaycush (Walbaum) and Salvelinus malma 

 (Walbaum). More detailed data of the occurrence of this species is given in 

 the following table: — 



