-,,gg CRUSTACEA. 



in the species examined. They are barely discerned in the water 

 without a glass. They differ from the preceding species also in the 

 falciform appendages to the beak; and the male anterior antennas 

 have not a geniculating joint. The large alimentary cavity is usually 

 filled with a bright red fluid, which makes the whole body appear red. 

 The caudal setae, as far as examined, are spinulous. 



Females were often observed with the bag of eggs attached. In 

 some specimens, the appendages or feet pertaining to the base of the 

 abdomen differ very much from the same organs in others (see the 

 two following species), and this difference is probably sexual, as all 

 females, known to be such by their bags of eggs, were of a similar 

 character in this respect. 



These species are confined to the open ocean. 



Setella tenuicornis. 



Antenna anticce fere corporis longitudine; articulis duobus basalibm 

 valde crassioribus, secundo oblongo, reliquis teretibus gracilUmk, tertw 

 fongisswio, quarto cum appendice instructo. Rami pedis antici biremis 

 subcequi, major 3-artmdatus, articulis fere cequis. Pedes abdominis 

 cum 5-6 setis elongatis subcequis instructi. Seta caudales corporefere 

 duplo longiores. 



Anterior antennae nearly as long as body; two basal joints quite stout, 

 the second oblong, others terete and very slender, the third longest, 

 the fourth with an appendage. Branches of first pair of natatories 

 subequal, the longer three-jointed, the joints nearly equal. Abdo- 

 minal feet with five to six elongate subequal setae. Caudal setas 

 nearly twice as long as body. 



Plate 84, fig. 1 a, animal, enlarged; a', beak, with appendages; b 

 base of anterior antennae; c, posterior antennae; g, first pair of feet, 

 claw not shown ; i, Jc, natatory feet of first and third pairs. 



Atlantic, latitude 7°-9*° north, longitude 21°-24° west, October 13 

 to 20, 1838. 



Length, one-fifteenth of an inch, exclusive of caudal setae. Colour, 

 pale bluish; in most specimens, the whole alimentary cavity is deep 



