1158 THE VOYAGE OF H.M.S. CHALLENGER. 



Cerapus sisrniihi, n. sp. (PI. CXXIV.). 



The Rostrum is acute, curving slightly downwards, prolonged beyond the small 

 lateral lobes of the head, which viewed from above appear to be acute, but are in fact a 

 little rounded ; the sides of the head emarginate behind the lateral lobes for the lower 

 antennae ; the back round, widening a little from the head to the third perseon-segment, 

 the pleon-segments narrowing successively to the telson. 



Tlie Eyes small, round, situated on the lateral lobes of the head. 



Upper Antennas a little shorter than the lower. The first joint larger, longer, and 

 much broader than the second or third, distally produced both above and below, below 

 into a pointed apex, above in a larger rounded process carrying some setules ; there are 

 also some small spines and setules on and near the lower process ; the joint is broadest 

 where the processes begin ; the second joint is broader than the third and a little longer, 

 with a small apical pointed process, the lower margin convex, carrying four groups of 

 spines, some of them long ; the upper margin has four or five setules ; the third joint with 

 setules on the upper margin and five groups of spines on the lower, the apical especially 

 very long ; the flagellum of five joints, together not equal to the second and third of the 

 peduncle, all armed with groups of spines and cylinders, the first joint having three groups 

 on its under margin. 



Loiver Antennas. — The first and second joints very short, the gland-cone inconspicuous; 

 the third joint a little longer than broad, with straight upper and convex lower margin, 

 carrying some small spines and spinules ; the fourth joint nearly as long as the first of 

 the upper antennae ; the fifth joint as long as the fourth but not so broad, the two armed 

 nearly as the second and third in the upper antennas ; the flagellum of four joints tipped 

 with strong spines, and also carrying groups of setae or very slender spines ; the four 

 together longer than the fifth joint of the peduncle. 



Upper Lip. — The distal margin evenly rounded. 



Mandibles. — The cutting edge divided into four or five unequal teeth ; the secondary 

 plate on the left mandible with four teeth, that on the right narrower, with an apical 

 tooth, above which the margin is only slightly denticulate ; the spine-row, as seen on the 

 left mandible, of three spines, distally much denticulate and bent backwards ; on the 

 right mandible there appear to be only two spines ; the molar tubercle a little pro- 

 minent, with the dentate crown pentagonal or almost circular, but decidedly flattened 

 on one edge which is the most strongly denticulate ; on the opposite border there is a 

 little laminar process, narrow at the base and widened distally ; there is a small round- 

 headed process near the base of the palp ; the first joint of the palp a little longer than 

 broad ; the second joint between two and three times as long as the first, with eight or 

 nine spines in five groups in or near the front margin ; the third joint very little shorter 

 than the second, distally a little broader, with a long feathered spine at the middle of 



