REPORT ON THE COPEPODA. 89 



conjunction with the rest. Amongst the Challenger species it will be seen that the six- 

 jointed apex occurs not infrequently with a two-jointed inner branch of the first foot, 

 though, as regards the character of the eyes, I am not able to speak certainly, owing to the 

 action of spirit on the specimens. 



* Head without lateral spines ; apex of posterior foot-jaw four-jointed. 

 1. Pontella acuta, Dana (PL XXXVI. figs. 1-12). 



Pontellina acuta, Dana, Crust. U. S. Expl. Exped., p. 1150, pi. Ixxx. fig. 12, a.-c. 



Length, l-6th of an inch (4 '2 mm.). Cephalothorax stout, cylindrical, posterior 

 angles strongly produced and spined, that of the right side in the male twisted (fig. 10); 

 head transversely sulcate in the middle, rostrum trifid, the two lateral segments larger 

 and curved slightly downwards, the central standing straight up, so as to appear single 

 when seen in front or behind. Anterior antennas (fig. 2) twenty-one-jointed, rather 

 longer than the cephalothorax, densely setose towards the base; that of the right side 

 (fig. 3) in the male has the central joints considerably swollen; the two denticulated 

 plates produced at the extremities, teeth short and stout (figs. 4, 5), those of the upper 

 plate acute, of the lower squared at the apices. Inner branches of all the swimming 

 feet two-jointed. The terminal spines of the swimming feet are somewhat dagger-shaped, 

 and have a wide pellucid outer border, which is very minutely pectinated ; the marginal 

 spines short, lancet-shaped, with pellucid, finely pectinated edges. Fifth pair of feet in 

 the female two-branched (fig. 9), both branches one-jointed, the outer twice as long- 

 as the inner, with three strong spines on the outer margin, and three at the apex ; inner 

 branch divided apically into two teeth. The fifth feet in the male (fig. 8) are unbranched, 

 that of the right side having the first two joints long and simple, the following joint 

 fan-shaped, and ending in a large pear-shaped claw; the three joints of the left side 

 are nearly simple, the third bearing three or four curved apical claws, and a stouter 

 one on the outer margin ; the inner margin is fringed with delicate hairs. Abdomen 

 of the female three-jointed, of moderate length, not quite half as long as the cephalo- 

 thorax, last joint about equal in length to the caudal stylets ; last joint of the male 

 abdomen scarcely half as long as the stylets. The first abdominal somite bears at the 

 apex of the right margin two spine-like processes, one of which in the female is very 

 large (fig. 11). Caudal segments about twice as long as broad; setae- subequal, shorter 

 than the abdomen. In the female the basal halves of the second, third, and fourth setse 

 (counting from the outside) are much dilated (fig. 12), the dilated portion of the second 

 gradually tapering away, those of the third and fourth ending abruptly ; all the setse 

 in their slender portions are densely plumose ; those of the male are all spathulate 

 towards the base, but not abruptly dilated as in the female. The anterior eyes are 



(ZOOL. CHALL. EXP. PART XXII!. 1883.) Z-ES 



