376 BULLETIN 140, UNITED ST/ ES NATIONAL MUSEUM" 



KEY TO SPECIES O^' HYSTKICHIS 



1. Only one circle of spines present ; it is directly posterior to mouth, the spines 



very large Hystrichis coronatus, p. 378. 



Numerous circles of spines, on head and cervical region if not on entire 

 body length 2. 



2. Spines of head and of cervical region of approximately the same size, or 



the latter smaller than the former 3. 



Spines of head and those of anterior part of body of different size, the latter 

 being longer and larger G. 



3. Head end with marked bulbous swelling Hystrichis cygni, p. 378. 



Swelling of head end not of marked bulbous nature 4. 



4. Spines of head comparatively sparce, only about 30 in each circle ; vulva 



not at tail end but 175/u. anterior to it ; eggs not pitted but with network 



of ridges Hystrichis acanthocephalicus, p. 377. 



Spines of head thickly set, about 50 to 57 in each circle ; vulva situated di- 

 rectly at anus; eggs pitted 5. 



5. Middle of body, at least in adult female, strongly swollen. 



Hystrichis tricolor, p. 376. 

 Entire body, even that of adult female, very slender. 



Hystrichis neglectus, p. 379. 



6. Spines, especially those of head, but also to a lesser extent those of cervical 



region, bent or crooked Hystrichis varispinosus, p. 387. 



Spines, as far as can be told from incomplete descriptions, straight 7. 



7. Female 100 mm. long by 3 mm. wide ; 17 spines in each circle on head ; 



from Fulica atra Hystrichis wedli, p. 381. 



Female 25 to 44 mm. long by 500/* to 1 mm. wide ; 23 spines in each circle 

 on head ; from Cygnus olor and litis faleincllus. 



Hystrichis orispinus, p. 381. 



The above key is a translation, with several modifications, of one 

 given by Jaegerskiold. 



HYSTRICHIS TRICOLOR Dujardin, 1845 



Synonyms. — Spiroptera tricolor (Dujardin, 1845) Diesing, 1851; 

 Spiroptera tadornae Bellingham, 1844. 



Hosts. — Primary: Anas boschas domestica, A. b. fera, A. tadorna, 

 Tadorna bellonii, T. tadorna; secondary : Probably fish, according to 

 Jaegerskiold. 



Location. — Glands of proventriculus. 



Morphology. — Hystrichis (p. 375) : Filiform worms, having the 

 anterior extremity of the body (fig. 437) armed with spines directed 

 posteriorly and arranged in 40 to 42 rows; on the head, where they 

 are the thickest, the spines number as high as 50 to 55 in each circle; 

 the largest spines are 40 to 50/a long. The exterior of the body is 

 white, the intestine black, and the intermediate portion and esopha- 

 geal region red. The mouth is round and somewhat protractile, 

 and there are six small buccal papillae. 



Male 25 mm. long. 



