158 M. T. Thorell on two European Argulidse. 



in the integument of the animal upon which the parasite has 

 fixed itself, and that the imbibed blood-corpuscles, on their way 

 through the narrow gullet, are broken and ground by the 

 mandibles. 



In those forms (for instance the species of the genus Gyro- 

 peltis) which lack maxillae, the mandibles are placed close to 

 the opening of the mouth, and may, being strongly toothed on 

 the lower border, unite the functions which we observe to be- 

 long to the mandibles and maxillae in A. foliaceus and the allied 

 species. 



Within both mandibles and maxillse other perfectly similar 

 mandibles or maxillse are usually perceptible, differing from these 

 only in being somewhat smaller. These are probably formed to 

 replace the older external organs when a change of the integu- 

 ment takes place : a similar supplemental structure is found 

 in the claw of the antennae of the first pair. In A. coregoni the 

 oral organs exhibit almost the same formation as in A. foliaceus. 

 A. purpureus differs especially in having the mandibles situated 

 lower down, close to the opening of the mouth, and in the 

 maxillse being destitute of teeth on their inner border. The 

 lip also has a different form. 



After these remarks on the morphology of the Argulidse we 

 pass on to the description of our two species, A. purpureus and 

 A. coregoni. 



II. 



Argulus purpureus, Risso *. 



Syn. Binoculus bicornutus, Risso. Hist. Nat. d. Crustaces de Nice, (1816) 



Agenor purpureus, Risso, Hist. Nat. d. princip. prod, de I'Europe 

 me'rid. torn. v. (1826) p. 139, pi. v. fig. 28. 



Scutum cephalicum maximum, oblongum, multo longius quam 

 latins, in lateribus parum rotundatum, antice utrinque pro- 

 funde sinuatum, postice anguste et profunde incisum, pedes 

 omnes totamque caudam tegens ; segmentum trunci ultimum 

 utrinque lamina foliacea prseditum ; cauda ampla, latissima, 

 dimidiam reliqui corporis longitudinem sequans, vix ad medium 

 incisa, laciniis acuminato-rotundatis ; stimulus longissimus; 

 sipho subcylindratus ; cotyledones parvi, diametro y^ longit. 

 corporis sequantes ; pecten plaga media scabra nulla, dentibus 

 tribus acutis ; pedes flagello carent. — Longit. circa 18, lat. 

 lOmillim. (?). 



Hab.xa. Mari Mediterraneo ad Nicaeam, in Selenia (Carangi) luna (Geoffr.) 



* Although the name bicornutus is older than purpureus, we prefer the 

 latter, on the ground that the former appellation is based on a false appre- 

 ciation of the antennae ; we have less hesitation in doing this, since no 

 personal right of priority is thereby affected. 



