140 



Gen. 6. Argissa, Boeck, 1870. 

 Syn : Chimseropsis, Meinert. 



Body highly compressed, glabrous, somewhat more slender in male 

 than in female. Cephalon of moderate size, without any rostral projection. 

 Coxal plates very unequally developed, the first 3 pairs rapidly decreasing 

 in size posteriorly; 4th pair, on the other hand, largely developed, especially 

 in the female, and nearly clypeiform. Metasome and urosome well developed, 

 especially in the male. Eyes of very simple structure, exhibiting on each 

 side a restricted number of small lenticular bodies imbedded at the periphery 

 of a common pigmentary mass. Both pairs of antennae rather slender and 

 only sparsely setous, the superior ones shorter than the inferior and provi- 

 ded with a small accessory appendage. Antennae of male more slender than 

 in female but without any trace of calceolse. Mandibles rather large, body 

 navicular in form, cutting edge well developed with both lamellae denticulate, 

 molar expansion large and protruding; between both a dense series of spini- 

 form bristles ; palp unusually small, but consisting of the normal number of 

 joints. First pair of maxillae with the masticatory lobe rather narrow, basal 

 lobe small, palp well developed, with the terminal joint expanded in its outer 

 part, and denticulate at the tip. Second pair of maxillae of the usual structure, 

 with both lobes about equal-sized. Maxillipeds with the masticatory lobe of 

 medium size and exhibiting interiorly a simple sharpened edge; 'palp narrow, 

 almost cylindric, dactylus slender spiniform. Gnathopoda similar in structure, 

 simple, not subcheliform, the propodos attenuated and without any distinctly 

 defined palmar edge. Pereiopoda nearly naked, the 2 anterior pairs very 

 small, the 2 succeeding ones with the basal joint moderately expanded; last pair 

 rather unlike the preceding ones, basal joint largely developed, the outer 

 joints partly laminarly expanded and edged with ciliated setae ; dactylus in 

 all very small. The 2 first pairs of uropoda normal ; last pair with the rami 

 foliaceous, the outer one having a very small spiniform terminal joint, inner 

 edge of both rami setous, the setae in male more developed than in female 

 and finely ciliated. Telson rather large, laminar and deeply cleft. 



Remarks. This is, unquestionably, the most anomalous of the genera 

 referred to the family Pontoporeiidae. Some characteristics seem, in fact, to point 

 to a closer relationship to quite a different family, viz, that of the Ampcliscidce, 

 and perhaps the genus should more properly have been referred to that 

 family, in spite of the presence of an accessory appendage to the superior 

 antennae. As, however, Boeck has regarded it as a true Pontoporeiid genus, 

 I prefer, provisionally, to accept his opinion. 



