NO. 1302. AMERICAN PARASITIC ARGULID^E— WILSON. 723 



wide as long; anal sinus broad, well rounded, cut nearly to the center; 

 papilla? basal. Sucking disks small, one-sixth the width of the cara- 

 pace, placed well forward and far apart; posterior niaxillipeds large, 

 well armed; basal plate narrowed anteriorl}^, triangular posteriorly, 

 with three sharp teeth. 



AntenniB normal. Swimming legs reaching far beyond the edge of 

 the carapace; lobes on the posterior pair very small, evenly rounded. 

 Flagella present, but no oviduct papilUe in the female. Abdomen in 

 the male considerably elongated, but no copulatory organs except the 

 regular peg and semen vesicle. Color a light green, becoming yellow- 

 ish where the carapace is thickened. 



Length 6-7 mm.; length of carapace 4.2-5 mm.; breadth of cara- 

 pace 3.5 mm.; length of abdomen 2-2.5 mm.; breadth 1.35 mm. 



Male about two -thirds this size; abdomen considerably elongated; 

 anal sinus triangular and cut more deeply. 



Habitat. — In fresh water almost all over Europe, both on the exter- 

 nal skin and in the branchial cavity of fish, including several species 

 of Gasterosteus., Chjprlnus carjno Linn^us, Ahramis hrama Cuvier, 

 LeucisGusrutilms Linnasus, Tincamilgaris Cuvier, Esoxlucius LinntBus, 

 PercafluvlatlUs Rondelet, Salmo trutta Linnaeus, and on the tadpoles 

 of Rana. 



ARGULUS PURPUREUS Risso. 

 Plate XXIII, tig. 05. 



Binoculus bicornutus Risso, 1816. 

 Agenor purpureus Risso, 1826. 

 Argulus purpureus Thorell, 1864. 



Carapace elliptical, much longer than broad, with the sides approxi- 

 mately parallel; posterior sinus narrow, extending fully half the 

 length of the carapace; antero-lateral sinuses deep. 



Abdomen orbicular, a little longer than wide, entirely covered by 

 the carapace; anal sinus narrow and slit like, extending to the center 

 of the abdomen; papilke basal; lobes acuminate orbicular. Sucking 

 disks small, one-fifth the width of the carapace, close together; pos- 

 terior maxillipeds lai'ge, well armed; basal plate rectangular, without 

 any central rough area; teeth sharp. 



Antenna3 strong, well armed. Swimming logs short, slender, 

 scarcely reaching beyond the carapace, lacking flagella; lobes on the 

 posterior pair narrow and long. No oviduct papillaj. Eyes small and 

 semilunar. 



This is the only species except versicolor which is at all highly colored. 

 Carapace pale blue-green, sparsely spotted with white; three violet 

 bands in either lobe, which widen and fuse anteriorly, while the two 

 inner bands are connected by a narrow line of the same color. Pig- 

 ment spots on the ovary violet and so arranged as to leave a median 

 line of pure white. 



