ON DREPANIDOTJINIA HEMIGNATHI. 619 



which are usually few in number; the outer limb (mauche) 

 of the forked base of the hooks is much longer than the inner 

 (garde), which is always slight; the point is directed backwards 

 when the rostrum is withdrawn. The majority live in the 

 intestines of aquatic birds. Their larva is a Cysticercoid, and 

 is found encysted in the bodies of small fresh-water Crus- 

 tacea." 



Railliet describes eight species of Drepanido taenia ; in one 

 of these the genital pores are on alternate sides of the body in 

 successive segments : the remaining seven species are unilateral 

 in this respect, but they fall into two groups, — one, with three 

 species, in which the number of hooks is eight ; and the other, 

 with four species, in which the number of hooks is ten. 



It is to this latter group that we must add the tapeworm 

 from H. procerus. The four species D. anatina, D. 

 sinuosa, D. setigera, and D. tenuirostris differ inter se 

 in several respects, but perhaps the simplest way of deter- 

 mining the species is by measuring their hooks. Of these four 

 species, D. hemignathi most nearly resembles I), tenui- 

 rostris, which occurs in certain of the ducks; it differs, how- 

 ever, markedly in size, being when mature about -5^ to ^^ the 

 length of the last named. It resembles D. tenuirostris in 

 the length of its hooks in the head, which in the latter are 

 20 — 23 ju, in the former are 18 to 23 ^; but whereas the hooks 

 of the embryo are about the same length in the new species, 

 i.e. about 20^, in D. tenuirostris they are but 7ju. The 

 neck is short, not long as in the last-named species, and the 

 eggs are small, about 40 — 50 ju in diameter, and spherical in 

 shape, not cylindrical as Krabbe^ figures them, with a length 

 of 85 ju. The hooks also differ in shape; those of D. tenui- 

 rostris have a much more strongly developed process corre- 

 sponding with the inner limb of the forked base than occurs in 

 D. hemignathi. 



The new species, which I have named after its host, may be 

 characterised as follows : 



• ' Danske Selsk. Skr.,' Bd. viii, 1S70, p. 249. 



