KEVIEW OF GENUS ARGULUS MEEHEAN 475 



Family ARGULIDAE 



Genus ARGULUS Muller 



KEY TO THE SPECIES OF ARGULUS 



. Anterior respiratory area prolonged laterally around posterior 



one (club shaped). 

 6'. Teeth of basal plate of second maxillae sharp, widely sepa- 

 rated ; suction cups supported by about 10 to 12 plates plus 

 an elongate segment ; posterior swimming lobe of fourth 

 appendage on female rounded, abbreviated on male; fresh 



water stizostethii (p. 479) 



h". Teeth of basal plate of second maxillae blunt, postmaxillary 

 spine small and blunt ; flagella present on first two swim- 

 ming appendages ; suction cups supported by 4 to 6 plates 

 plus an elongate segment ; respiratory area relatively nar- 

 row ; posterior swimming lobe on female prolonged into a 

 fingerlike projection, only slightly prolonged on male ; fresh 



water, Siam siamensis (p. 482) 



'. Smaller respiratory area anterior, mesial, or in an anteromesial 



notch of larger area. 

 6*. Entire smaller respiratory area anterior to larger. 

 c\ Teeth on basal plate of second maxillae sharp, distal one 

 more widely separated than other two ; ribs of suction cups 

 composed of 10 to 12 plates and an elongate segment ; 

 carapace just reaching third thoracic appendages ; anterior 

 hook on antennae slight or lacking, second antennae long ; 

 last thoracic segment very wide, flaring over abdomen ; 



brackish and salt water alosae (p. 481) 



<?. Basal iilate of second maxillae lobed or with slender blunt 

 teeth. 

 d\ Tips of maxillary teeth blunt, but plate not lobed. 

 e^. Ribs of suction cups supported by rods. 

 f. Ribs of suction cups composed of 3 rods ; knob or 

 hook lacking on anterior surface of first antennae ; 

 swimming lobe of fourth appendages boot-shaped, 

 heel pressed against end of thorax, toe extending 

 to or beyond edge of abdomen ; whole body appear- 

 ing circular ; anterior respiratory area minute, 

 posterior one very large and oblong; salt water, 



Siam, Java indicus (p. 483) 



f. Supports of suction cups composed of 4 to 6 rods, 

 distal ones may be compressed ; anterior hook pres- 

 ent on antennae, a seta two-thirds as long as two 

 distal segments of second antennae, and opposing 

 them, a long seta opposing tip of first antennae; 

 slight posterior lobe on fourth appendages rounded 



or faintly boot-shaped ; fresh water fiavescens (p. 484) 



el Suction cups supported only by imbricate plates or by 

 plates and a long basal segment. 

 f. Suction cups supported only by imbricate plates ; spine 

 at base of first antennae and near midline of body 

 (postantennal) broad and blunt. 



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