PARASITIC ROUNDWORMS 



549 



set off from the neck. In the type species, FUicollis anatis, a European form not yet definitely 

 reported for North America, the adult female has the proboscis enlarged to a thin-walled 

 spherical bladder which bears the hooks on its anterior aspect in a series of radiating lines. 



Representative North American species. 



FUicollis botulus Van Cleave 1916. 



This peculiar form found in water birds has been reported from the eider (Somateria dresseri) 

 from Maine. Although the range of the bird carries it (rarely) as far west as Colorado, yet 

 the particular parasite may not be native to fresh waters. Acanthocephala of this general 

 type have been reported from North American ducks under the name of " Echinorhynchus 

 poiymorphus." 



FIG. 852. FUicollis botulus. Female with tip of proboscis slightly inturned. X 10. Male, neck re- 

 tracted, body spines not shown. X 17- (After Van Cleave.) 



23 (20) Body club-shaped, anterior end enlarged. Proboscis bent ventrad, 



forming an angle with axis of the body. Spines extend 

 further posteriad on ventral surface than on dorsal. 



Corynosoma Luhe 1904. 



The peculiar form and the unusual distribution of spines on the body serve to identify the 

 members of this genus which is apparently limited in the adult stage to fish-eating birds and 

 mammals, chiefly seal. The genus is mainly marine but Van Cleave has a record of a species 

 from birds at Yellowstone Lake. 



24 (13) Proboscis sheath attached at center of proboscis. 



Family CENTRORHYNCHIDAE Van Cleave 1916 . . *5 



The proboscis sheath starts from near the center of the proboscis wall. The mature forms 

 are parasitic in the intestine of birds. 



25 (26) Proboscis receptacle two layered: retractors penetrate its posterior 



rounded tip .;;:.. Centrorhynchus Liihe 1911. 



Three long tubular cement glands. 



Only North American species. 



Centrorhynchus spinosus Van Cleave 1916. 



Female 20 mm. long, 0.6 mm. broad anteriorly, 0.5 

 mm. posteriorly. Proboscis 0.65 mm. long constricted at 

 insertion of proboscis receptacle with hooks of 2 types in 

 30 longitudinal rows of about 24 hooks each. 



In intestine of Herodias egretta from District of Colum- 

 bia (?). 



FIG. 853. Centrorhynchus spinosus. Proboscis and anterior 

 region of body, showing also insertion of proboscis receptacle 

 and location of the retractors of the receptacle with reference 

 to the wall. X 26. (After Van Cleave. ) 



Proboscis receptacle single layered; retractors pass through its sides 

 some distance anterior to posterior tip. 



Mediorhynchus Van Cleave 1916. 



Nerve ganglion near center of proboscis receptacle. In male 8 round or pyrifprm cement 

 glands. Proboscis hooks distinctly of two types. Proboscis receptacle not cylindrical in form. 

 Known species mostly in land birds but one record concerns the Carolina rail, Porzana Caro- 

 lina, that might have been infected from an aquatic intermediate host. 



26 (2 5 ) 



