NOTODELPHYS. 127 



marginal segments, all of which have stout apical 

 setse, the stronger ones being plumose or pecti- 

 nated, last three joints very small ; posterior foot- 

 jaws (fig. 7) slender, 3- jointed, with several plu- 

 mose marginal setas, that arising from the second 

 joint being much the strongest ; the terminal joint is 

 very small, the penultimate much larger, and the 

 first three or four times as large as the second. The 

 first pair of swimming feet (fig. 8) has the external 

 margin of the first joint of the outer branch fringed 

 with short strong hairs (" dentibus angustis, dense 

 serratus," Thorell) ; the margins of the two following 

 joints, as well as those of the inner branch, are 

 perfectly smooth ; in the following pairs of feet, how- 

 ever (fig. 9), all the joints of the inner, as well as the 

 first of the outer branch, are finely fringed on their 

 external borders ; all the setse are very finely plumose 

 (much more finely than could be shown in the 

 engraving). The fifth pair of feet (fig. 10) are com- 

 posed each of two 1- jointed branches, the outermost 

 of which is of oblong subquadrangular outline, and 

 bears a long spine at the apex, and a short tooth-like 

 process on the inner margin ; the inner branch is 

 broader and shorter, and has two apical setae, the 

 innermost of which is stout and spine-like ; there are 

 also four small teeth on the inner margin ; the 

 peduncle of the foot is armed at its inner angle with a 

 row of about six small spines. Caudal segments 

 about once and a half as long as the preceding 

 abdominal ring ; the small lateral setas situated a little 

 below the middle of the external margin ; internal 



