bUtrSTACEi l^i^ttmb^kr^ 



^n Account of the Crustacea of the United States. S(f 

 Tliomas Say. Read July 7, 1818., 



rcontinued.5 



Genus GAMMAllUB. 



%ody thirteeii-jointed exclusive of tlie Iiead^ and in- 

 t^ludiiig the tliree-jointed tail : antennm with the la^ 

 joiat composed of uumeroua minute ones, superiores as 

 ?ong or longer than the iftferiores, four- jointed, penul- 

 timate joint witii a seta at the apex, inferiores five-joint- 

 VmiI ; feet fourlcen, the two anterior pairs monodactyl^ 

 subefjual, hands oval, third and fourth pairs gmallest; 

 iail with small fasciculate spines above and bifid ones 

 ^t tip. 



sPECu:&. 



1. (y. ^fasciatus. Body Avbitish, translucent, with 

 t)3)solete greenish bands ; eyes renifoiin, situated iii^ 

 ^hc outer base of the antennas, terminal joint of i\\^ 

 superior autennsa with about thirty articulations, 



Juhahits the larger streams of fresh water. 



Cabinet of the Academy. 



Jhdy piiiictiired, fasclate with faint green, whiok 

 %fter death becomes of a rufous colour ; sujjerior an- 

 lanncEy second joint annulate with ferruginous, seta 

 'attaining the tip of the fiuh articulation of the termimS 

 ^'oiiit, lerminal joint with iroin twenty-five to thirl j ar^ 

 '^)cuktb]i3 ihifcviov aTiteunce hairy, second and thiili 



