CRUSTACEA. 627 



We have already noticed this genus (p. 575). It was regarded by LOVN, 

 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 LOVEN gives to 

 the genus are: Corpus molle, depressuin, discoldeum; proboscis retractilis 

 mutica; anus discretus ori oppositusj bothria later alia opposita; pedesinferi, 

 articulati, hamiferi; genilalia mascula duplicia mutica. There are different 

 known species of these animalcules, living parasitically on Comatulce, 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 LEUCKAKT Zoolo- 

 gische BruchstucTce, in. 184-2, pp. 5 12, LOVEN, ERICHSON'S Archiv f. 

 NaturgescJi. 1842, s. 306 foil, or Ann. des Sc. nat. 20 SeVie, xvm. Zool. 

 pp. 291 298. 



Family IV. Ergasilina. Ceplialothorax large. Abdomen arti- 

 culate, made up of many segments. Two or four antennas. 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 MILNE EDWARDS at 

 first placed the genus Nicoikoe, 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 LEACH. Superior antennas sex-articulate, setaceous; 

 inferior antennas uncinate. Mouth produced into a rostrum. Ce- 

 Iphalothorax oval. Two foliaceous laminae at the back behind the 

 | cephalothorax, and three pairs of laminae under the abdomen, in 

 I place of natatory feet. 



Sp. Anthosoma Smithii LEACH, Caligus crassus ABILDGAARD, STcrivter of 

 Naturhistorie Selskalet. m. 3, 1794, p. 49, Tab. v. figs, i 3, DESMAREST 

 Cons. gen. s. I. Crust. PI. 50, fig. 3 ; in the mouth and on the gills of sharks. 



Nemesis Eoux. 



Fig. GUERIN Iconogr., Crust. PI. 35, fig. n. 



Dichelesthium HEKM. Anterior antennas with seven joints, 

 itaceous, reflected backwards ; posterior antennas forcipate, resem- 

 )ling two frontal chelae, with internal finger moveable. Cephalo- 

 fhorax cordate, truncated anteriorly. Two mandibles denticulate 

 apex, setaceous, between the folds of rostrum, and two palps 



402 



