CRUSTACEA. 627 
We have already noticed this genus (p. 575). It was regarded by Lovén, 
who has treated of its structure most exactly, as a form of transition 
between the Trematodes and the ringed worms. I think that the short 
jointed feet militate against this disposal of it. The surface beset with 
vibratile cilia would seem to remove it from the crustaceans, with which 
however it has the most affinity. The characters which Lov&éN gives to 
the genus are: Corpus molle, depressum, discoideum; proboscis retractilis 
mutica; anus discretus ori oppositus ; bothria lateralia opposita ; pedes inferi, 
articulati, hamiferi ; genitalia mascula duplicia mutica. There are different 
known species of these animalcules, living parasitically on Comatule, only 
one or two lines in size, of which one is distinguished by conical cirri, twenty 
in number, at the margin of the disc of the body. See Leuckart Zoolo- 
gische Bruchstiicke, 111. 1842, pp. 5—12, Lovin, Ericuson’s Archiv f. 
Naturgesch. 1842, s. 306 foll. or Ann. des Sc. nat. 2e Série, xvit. Zool. 
pp: 291—208. 
Family IV. Hrgastlina. Cephalothorax large. Abdomen arti- 
culate, made up of many segments. ‘Two or four antenne. Mostly 
four pairs of abdominal feet (natatory). 
In these parasites the similarity of form with the genus Cyclops 
is very conspicuous, so that even AuDoUIN and Minne Epwarps at 
first placed the genus Vicothoé, discovered by them, with the Mono- 
culina. 
A. Body elongate. Two filiform receptacles of eggs, at the 
posterior extremity of body. Uncinate feet behind the rostrum. 
Anthosoma Leacu. Superior antenne sex-articulate, setaceous; 
inferior antenne uncinate. Mouth produced into a rostrum. Ce- 
phalothorax oval. ‘Two foliaceous laminew at the back behind the 
cephalothorax, and three pairs of lamina under the abdomen, in 
place of natatory feet. 
Sp. Anthosoma Smithii Leacu, Caligus crassus ABILDGAARD, Skrivter of 
Naturhistorie Selskabet. 111. 3, 1794, p. 49, Tab. Vv. figs. 1—3, DESMAREST 
Cons. gén. s. l. Crust. Pl. 50, fig. 3; in the mouth and on the gills of sharks. 
Nemesis Roux. 
Fig. Guér1n Iconogr., Crust. Pl. 35, fig. 11. 
Dichelesthium Herm. Anterior antenne with seven joints, 
setaceous, reflected backwards; posterior antennze forcipate, resem- 
bling two frontal chele, with internal finger moveable. Cephalo- 
thorax cordate, truncated anteriorly. Two mandibles denticulate 
at apex, setaceous, between the folds of rostrum, and two palps 
40—2 
