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



follows at some distance the anterior margin of the segment ; the first epimera are not 

 divided by any transverse suture ; the epimera of the three succeeding segments are 

 separated from their terga by a suture. 



The cephalic shield lias a crescentic ridge between and a little in front of the eyes 

 as in Serolis tubervulata (cf. PL VI. fig. 1) and other species ; its anterior margin is pro- 

 longed in the median line into a short rostrum, and as in other species a ridge separates 

 off the antero-lateral portion from the rest. 



The caudal shield is trifid at its extremity, and furnished with a central carina which 

 runs from end to end ; on either side of this are two lateral caringe, which do not extend 

 along the whole length of the caudal shield, they terminate behind at some distance from 

 the end of the caudal shield in freely projecting spines ; the inner pair extend farther 

 back than the outer pair ; another carina runs parallel with the anterior margin of the 

 caudal shield on either side, and terminates close to the articulation of the uropoda. The 

 lateral margins of the caudal shield, as well as of the posterior epimera, are denticulate. 

 A noticeable character of this species is the prolongation of the abdominal epimera a little 

 way beyond the last pair of thoracic epimera ; in Serolis minuta the same thing occurs, 

 but in these two species only. 



T\iQ first pair of antenna are a little shorter than the second pair; the filament, which 

 has about eighteen joints, is rather longer than the basal portion of the antenna, — the 

 latter is composed of four joints; the first is short, the second about twice its length, and 

 about equal in length to the succeeding joint, though considerably stouter than it. 



In the second pair of antenncB the two distal joints of the stem are the longest, and 

 about equal in length to each other ; they are somewhat bow-shaped, and the anterior 

 margin is beset with tufts of long hairs, five to each joint in the specimen from which the 

 description is taken ; the filament has twelve or thirteen joints. 



The mandibles show the usual asymmetry; the left mandible has a chisel-like cutting 

 process, the edge of which is somewhat crenate in outline ; this structure is absent from 

 the right mandible. 



The first pair of maxillce consist as usual of a basal piece with which are articulated 

 two masticatory lobes ; the posterior of these is delicate and small, and l:)ears one short 

 spine at its expanded distal extremity as in Serolis p>aradoxa {cf PI. V. fig. 14). 



The second pair of maxillai are comparatively large; the middle lobe is furnished with 

 four spines upon the cutting margin instead of the usual two. 



In the maxillipedes the stipes and lamina are completely separated by a suture ; the 

 second joint of the palp is not so markedly heart-shaped as in other species. 



In the second jMir of thoracic appendages the sixth joint is entire ; the fifth joint has 

 a row of spines upon the inner side, they are as usual of two kinds ; the longer spines 

 terminate in a bifid extremity, of which the anterior bifurcation is the longest ; the axis 

 of the spine extends between the two branches, and is rather lono-er than either. 



