ARGULUS. 227 



Genus ARGULUS Matter, 1785. 



Body flattened, cephalothorax scutiform; cephalon 

 and first thoracic segment coalescent ; other segments 

 free. Abdomen small, comparatively narrow, and 

 ending in two equal lobes, unsegmented. Antennae 

 two pairs, small, first pair tolerably stout and termi- 

 nating in a small hook. Mouth siphon-like, enclosing 

 a flexible, sharp-pointed, sting-like process furnished 

 with a poison-gland. Two pairs of maxillipeds, the 

 first pair transformed into sucking-discs; posterior 

 pair prehensile, their integument rough with minute 

 prickles, and having a tridentate plate on the inferior 

 aspect of the basal joint. Swimming-legs four pairs, 

 biramose, and furnished with plumose hairs. Females 

 without external egg- strings. Eyes conspicuous. 



1. Argulus foliaceus (Linn.). 

 (Plate LXXII, figs. 1-10.) 



1758. Monoculus foliaceus Linn. Systema Naturae, 10th edit., vol. i, 

 p. 634 



1762. Sinoculus gasterostei Geofroy. Insectes de Paris, vol. ii, p. 661. 



1785. Argulus foliaceus Miiller. Entomost., p. 123. 



1785. Argulus charon idem. Ibidem, pi. 20, figs. 1, 2. 



1793. Monoculus arguluso Fabr. Entom. Syst., vol. ii, p. 489. 



1798. Monoculus gyrini Cuvier. Tab. element. Hist. Nat., p. 45. 



1802. Ozolas gasterostei Latreille. Hist. Nat. Crust, et Ins., vol. iv, 

 p. 128, pi. 29, fig. 4. 



1814. Argulus argulus Leach. Edin. Encyclop., vol. vii, p. 388. 



1839. Argulus foliaceus Thompson. Ann. and Mag. Nat. Hist., vol. v, 

 p. 221. 



1845. Argulus foliaceus Yogt. Nouv. Mem. Soc. Helvet.,vol. vii, pi. i, 

 fig. 2. 



1850. Argulus foliaceus Baird. Entorn., p. 255, pi. xxxi, figs. 1, 2 a-l. 



Carapace of a rounded oval shape, rather longer 

 than broad, and with the front margin slightly pro- 

 jecting forward ; posterior sinus narrow and extending 

 forward for about two-fifths of the carapace. Abdo- 

 men small, rather longer than broad, and about one- 

 fourth the length of the cephalothoracic shield ; lobes 

 bluntly rounded at the end, separated by a sinus 

 extending forward to about half the length of the 



