163 M. T. Thorell on two European Argulidse. 



Selenia luna (Geoffr.), Bonap. {le Caranw magnifique, Citula 

 Banksii, Risso), commonly attached to the base of the pectoral 

 of that fish. The female was unknown to him : the male is 

 distinguished by " deux petits tubercules coniques, blanchatres 

 .... situes k la base de la derniere paire de pattes.^' In colour 

 it is said to be " d^un pourpre violdtre, traverse par six lignes 

 longitudinales paralleles, blanchatres." The description in * Hist. 

 Nat. d. Crustaces de Nice' is extremely detailed, but contains 

 many inaccuracies. The description in ' Hist. Nat. d. princ. 

 prod, de I'Europe merid.' would seem to be only an abstract of 

 the former. It is accompanied by a figure, in which it is not 

 easy to recognize an Argulid. In his first-mentioned work, 

 Risso gives correctly the affinities of the animal, and places it in 

 Geoffroy's genus Binoculus, under the name of B. bicornutus. 

 But in the later work we search in vain for either Binoculus or 

 Argulus', with his usual superficiality, Risso there removes the 

 animal to the family Bopyrida, under the name of Agenor (n. g.) 

 purpureus, by the side of species of the genera Bopyru^ and Ce- 

 crops ! A. purpureus deserves, more than any other species of 

 Argulus, to be made the type of a distinct genus {Agenor, Risso). 

 Besides the unusual development of the head shield, it is espe- 

 cially characterized by the absence of the " tassel " or flagellum 

 (" gissel ") on the anterior pairs of legs, as also by the two 

 lamellse on the last segment of the trunk. The parts of the 

 mouth also show a somewhat different structure, as does the 

 second pair of maxillipeds, in the peculiar " patella " which is 

 inserted between the second and third joints of these limbs. 



Argulus coregoni, n. sp. 



Scutum cephalicum antice utrinque subsinuatum, in ? inverse 



subovatum, vix longius quam latius, pedes ultimi paris non 



tegens, in <^ amplissimum, suborbiculatum, laciniis apice se 



invicem at omnes pedes tegentibus; cauda ovata, longitudine 



^ reliqui corporis superans, saltem ad medium incisa, laci'niis 



apice lanceolato-acuminatis; art. Pantenn. secundi paris dcnte 



minuto armatus ; stimulus minutus ; sipho subcyhndratus ; 



cotyledones sat parvs, diametro ^-^ longitudinis corj)oris 



sequantes ; pecten plaga media oblongo-rotundata scabra, 



dentibusque 3 conicis, acuminatis. — Long. $ usque ad 13, 



latit. ad 8^ millim.; ^ longit. 10|, latit. 8 millim. 



Hab. in lacubus majoribus Suecise mediae et septentrionalis ; in Storsjon 



aliisque lacubus Jemtlandiae a Dr. C. L. Nystrom in Coregono lavareto 



Linn, et Thymallo vulgari Nilss. inventus ; in Laxsjbn Dalslandiai in 



Coregono lavareto et in lacu Vettern in Suimone trutta Linn, a Dr. H. 



Widegren quoque captus. In cute externa piscium parasitat. 



Descr. Femin^. Corpus in universum eadem est forma atque in 

 A.foliaceo : ovatum, depressura, supra modice convexum. Scutum 



