C YCLOPOIDEA. 



1193 



Abundant at sea, off Rio Negro, east coast of South America, 

 January 25, 1839, 5 h., a. m. 



Length, one-twenty-fourth of an inch. Colourless. Length of 

 cephalothorax, much more than twice its breadth or nearly three 

 times; last three segments nearly half the anterior. Antennse have 

 usually a double curvature and extend laterally with the tips hardly 

 in advance of the beak ; setae on anterior margin near base short, 

 and stout, and crowded; large joint naked (?). An extremity of a 

 maxilliped, or perhaps the mandibular palpus, was observed, as shown 

 in fig. e; it terminates in one or two straight setae. Abdomen much 

 shorter than cephalothorax. The abdominal segments decrease in 

 width from the basal, the last being hardly one-fourth as broad as the 

 first. The appendage to base of abdomen below is short, and has one 

 or two short setae at extremity. 



Rarpacticus acutifrons, Dana, Proc. Amer. Acad. Sci., i. 153. 



Genus CLYTEMNESTRA. 



Frons subrostratus, appendicibus nullis. Antennce anticce flexiles ; maris 

 non subcheliformes nee articulatione geniculantes. Pedes antici per- 

 magni, subcheliformes. 



Front subrostrate, appendages none. Anterior antennae flexible ; in 

 male not subcheliform, not having a geniculating joint. Anterior 

 feet very large, subcheliform. 



This genus embraces such of the Harpacticinae as have the male 

 antennae not distinctly geniculating, and the first pair of legs very 

 large subcheliform. 



The genus Harpacticus may contain species with large subcheliform 

 anterior feet, like Clytemnestra. But the anterior antennae of males 

 are always geniculating. These organs are very similar in form to 

 those of Setella ; the setae are rather long in the species observed, 

 and the fifth joint is slightly arcuated. 



Clytemnestra, Dana, Proc. Amer. Acad. Sci., i. 153, 1849. 



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