,-jqo CRUSTACEA. 



A specimen was collected in the Paumotus, August 13, 1839, which 

 is probably a female of this species. The head is narrow. Eyes on 

 one and the same minute red spot. Cephalothorax obtuse behind. 

 Antennae distinctly longer than the body, the two nearly in a straight 

 line, very slender, apical joint longer than penult. Abdomen four- 

 jointed, the second large, inflated, gibbous below. Stylets about half 

 the abdomen in length, divergent ; setae about as long as abdomen. Five 

 pairs of natatories, the posterior pair much like the preceding, but a 

 little smaller. 



Cyclopsina tenuicornis, Dana, Proc. Amer. Acad. Sci., Boston, ii. 25. 



Hemicalanus gracilis. 



Maris :— Antennae anticce corpore valde lo?igiores; abdomen i-articulatum ; 

 aliis C. tenuicorni similis. 



Male .—Anterior antennas much longer than the body. Abdomen four- 

 jointed. In other characters near the G. tenuicornis. 



Plate 78, fig. 12a, animal, enlarged; b, extremity of female an- 

 tenna, or of left of male. 



Collected in the Pacific, May 14, 1841, latitude 25° north, longitude 

 167° east. 



Length, one-sixteenth of an inch. Colour, in part reddish. 



This species may possibly be only a variety of the tenuicornis. 

 The length of the antennae is not constant. In one specimen they 

 were one and one-third times as long as the body, extending beyond 

 the stylets as far as the whole length of the abdomen ; in another they 

 were one and one-fifth times as long as the body. The cephalothorax 

 narrows anteriorly, as in the two preceding species, and has about the 

 same form. The branches of the posterior antennae are not as unequal 

 as in the tenuicornis, yet the one with two subequal joints is the 

 longer The setae of the anterior antennae towards the base are 

 generally three or four times as long as the diameter of the joints. 

 The part of the right male antenna beyond the geniculating articulation 



