1094 CRUSTACEA. 



than the basal; a third and fourth, each half shorter than the second 

 and stout; the fourth, bearing a stout spine or claw (nearly straight) 

 at apex, nearly or quite as long as itself; and the second giving 

 origin within to a long, naked, and stout seta, which extends beyond 

 the apex of the terminal spine or claw. The whole has nearly the 

 shape of a letter N, the second joint constituting the oblique line in 

 the letter, and the third and fourth joints together one of the legs. 

 The left of this pair of feet is simple and unflexed. 



Undina simplex. 



Frons obtusus. Cephalothorax posticd rotundatus, 5-articulatus, segrnmto 

 ultimo breviore. Antennce anticce corporis longitudine, articulo primo 

 elongate; setis perbrevibus, seta a/rticuli secundi longiusculd, flexd, 

 setis penuliimis rectis et articuli longitudine, posticd antepenidtimd 

 dimidio lemgiore, apicalibus minutis, und uncinatd. Abdomen b-arti- 

 culatum. Styli caudales perbreves; setce plumosce, 2dce duplo longiores. 



Front obtuse. Cephalothorax rounded behind, five-jointed, last seg- 

 ment short. Anterior antennae as long as the body, first joint 

 oblong; setae very short, on second joint a longish bent seta; the 

 posterior antepenult setae equalling last two joints of antenna in 

 length, the anterior and posterior penult half shorter, straight; the 

 apical shorter than joint, one uncinate. Abdomen five-jointed. 

 Caudal stylets very short, setae plumose, second more than twice the 

 first. 



Plate 77, fig. 9 a, view, enlarged; b, extremity of antenna. 



Collected, March 25, 1841, in the Pacific, off El Gran Cocal, south 

 of the Kingsmill Islands, latitude 5° 45' south, longitude 175° 30' 

 west; also, May 14, 1841, latitude 25° north, and longitude 167° east. 



Length, one-twentieth of an inch. Colourless. 



This species is near the preceding, and may be the same. Yet it is 

 retained as distinct, as there are four posterior joints to the cephalo- 

 thorax and the setae of the antennae are different; the basal joint is 

 longer, and the longish bent seta is attached to the second joint. 



