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



of irregularly triangular form, with the dorsal line gradually declining anteriorly, and 

 the posterior edge somewhat elevated in the middle. The pseudorostral projection is 

 rather produced and sharply pointed, a little longer than the frontal lobe, and quite 

 horizontal. The inferior edges of the carapace are strongly arcuate in the middle, and 

 densely denticulate throughout ; posteriorly they join the posterior edge without forming 

 any angle, and anteriorly they ascend more perpendicularly to the base of the pseudo- 

 rostral projection. As seen from above (fig. 2) the posterior half of the carapace is of 

 about uniform breadth, whereas the anterior rapidly tapers to a conical point. The 

 surface of the carapace is somewhat irregularly grooved, a slight furrow running 

 obliquely along each side from the frontal lobe backwards. It is densely armed all over 

 with sharp anteriorly directed spines, some of which are much larger than the others, 

 and rather regularly arranged on each side of the middle line, especially on the dorsal 

 surface. In young specimens the difference in size between the spines is still more 

 pronounced than in the adult. The eye would seem to be imperfectly developed, as 

 neither pigment nor distinct refracting bodies could be detected within the rounded 

 ocular lobe. 



The five exposed segments of the trunk are rather sharply defined and armed with 

 scattered spines, forming more or less distinct transverse rows; on each segment two of 

 the spines arranged in pairs dorsally are somewhat larger than the rest. The epimeral 

 plates on all the segments are strongly denticulate at the edges; those of the last 

 segment are obtusely rounded. 



The tail exhibits the usual slender form and the peculiar nodose shape of the seg- 

 ments characteristic of the present genus. Like the rest of the body, it is more or less 

 densely spinous, especially on the dorsal surface, the number of spines varying in 

 different specimens. 



The antennulse (see fig. 3) are rather slender, with the two outer joints of the 

 peduncle unusually elongate, and, taken together, considerably longer than the basal 

 joint. The latter is armed on the lower surface at the extremity with two strong- 

 spines, and exhibits, moreover, as in the preceding species, two setse, the inner pointing 

 anteriorly, and densely hairy, the outer recurved and quite smooth, and longer than 

 usual. Of the two outer joints of the peduncle, the first is by far the longer. The 

 flagella are comparatively small, the outer scarcely attaining the length of the last joint 

 of the peduncle, and the inner very minute, being about one-third as long. 



The antennae (ibid.) are also somewhat smaller than in the preceding species, each 

 forming a regularly tapering stem divided into four articulations, each with a single 

 ciliated seta at the end. 



The first pair of legs (fig. 4) are comparatively slender, and when fully extended, 

 considerably exceeding the carapace in length. The small coxal joint is bordered with 

 a row of strong denticles, and the curved and elongate basal joint also exhibits a number 



