80 CRUSTACEA COPEPODA. II. 
Herpyllobius Stp. & Ltk. (Silenium Kr.). 
All specimens from our area are referred to a single species, H. arcticus. Whether the two other northern 
species, H. crassivostris M. Sars and H. affinis H.J.H., are valid may be doubtful, but these questions cannot 
be finally settled without a most detailed examination of the appendages and their sete of the larval males. 
98. Herpyllobius arcticus Stp. & Ltk. 
1861. Herpyllobius arcticus Steenstrup & Liitken, K. Danske Vid. Selsk. Skr. 5. Reekke, naturh. og math. Afd. 
5. B. p. 426, Tab. XV, fig. 40 «, 407, 400 (not 40 £). 
1863. Silenium Polynoés Kroyer, Nat. Tidssk. 3. Rekke, Bd. II, p. 403, Tab. XVIII, fig. 6, a—g. 
1877. Herpyllobius arcticus Levinsen, Vid. Medd. Naturh. Foren. i Kjobenhavn, 1877, p. 363, Tab. VI, 
Fig. 12—18. 
1892. -— — H.J. Hansen, Entom. Medd. udgivne af Entom. Foren. i Kjgbenhavn, 3. B., 
p. 227—231. 
1900. — — Soren Jensen, Overs. Kgl. Danske Vid. Selsk. Forhandl. 1900, p. 84, Tab. I, 
Fig. 8—g, Tab. II, Fig. 1o—18. 
1900. = —  H. J. Hansen, Danmarks Stilling og Tilstand, II. Det Kgl. Danske Vid. Selskab; 
med Tilleg, p. 124—205. 
1912. — — Kathleen Haddon, Quart. Journ. Microsc. Sci., Vol. 58, pt. 2, p. 385—410, Pl. 22 
and 4 Text-figures. 
In this synonymical list the more important publications as to Herpyllobius arcticus (and the family 
Herpyllobiidee) are enumerated. The animal was first mentioned, without name, by Kroyer (1838); other 
papers dealing with this vexed topic or stating new localities have been written by Steenstrup (1869), M. Sars 
(1870), Kroyer (1870), Schiddte (1870), M’Intosh (1874), Claus (1875), H. J. Hansen (1886(1887) and 1897), 
Giard & Bonnier (1893), Gravier (1912), K. Stephensen (1912, 1913 and 1916). The papers from 1838 to 1912 
written by all these authors may be found noted either in Kathleen Haddon’s above-named treatise or in 
K. Stephensen’s “Conspectus”’, 1913. 
The material from the “Ingolf” area seen by me is very large, comprising specimens from nearly 
thirty localities. All the hosts preserved belong to the genus Harmothoé; most of them to H. imbricata L., 
but some among them to H. vavispina Sars; besides parasites have been found on 2 specimens of H. mollis 
Sars, and on a single specimen of H. aspera Arm.-Hansen'. Some authors state that it has also been found on 
a few other Annelids (see ‘‘Occurrence”’ and “Distribution’’). 
The majority of the specimens of this parasite are found on the upper surface of the head of small 
specimens of the host, but sometimes also on good-sized or large hosts; in a few cases 2 parasites are found 
near each other on the same head. Sometimes a single parasite or even 2 parasites may be observed on the 
body in front of or behind its middle, but at or just above the parapodia. Generally the parasites have their 
external body subglobose and the ovisacs most frequently not much longer than broad, but sometimes the 
1 The major part of the hosts has been determined by Mag. sc. H. Ditlevsen. 
