310 HISTORY OF BRITISH CRUSTACEA. 



Dr. Baird says : " The mouth-apparatus consists of a large 

 well- developed sucking-tube and appendages, adapted for 

 puncturing the skin of the animals upon which they live as 

 parasites, and for sucking the juices of their bodies; and 

 three pairs of foot-jaws, constructed for enabling them to 

 fix themselves upon their prey." When young they undergo 

 a series of metamorphoses. 



Fam. ARGrTJLIDM, Leach. 

 Head like a large circular-shaped shield. Antennse short, 

 thick, two-jointed ; second pair of foot-jaws replaced by a 

 pair of large suckers. (Plate XIX. fig. 1 a, b.) 



Gen. 171. AKGULUS, Matter. 



Argulus folia ceus, Linn. sp. Fish Argulus. (Plate XTX. 

 fig. 1.) — Eounded-oval ; carapace notched on either side 

 in front, transparent, slightly greenish, and marked on both 

 sides by branched veinings of darker hue. 



Hab. On various kinds of fresh-water fish in the neigh- 

 bourhood of London : it is most commonly met with on the 

 stickleback. 



Dr. Baird says, it " is an exceedingly pretty and graceful 



