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



the hind margin sloping irrcgukrly backwards, to form an acute angle with the convex 

 lower margin. The branchial vesicles narrow above and below, longer than the first 

 joint of the limb, the distal end bending a little forwards. The first joint reaching 

 beyond the side-plate, wider below than above, with three spines on each margin ; the 

 second joint with one spine at the hinder apex; third joint about as long as the wrist, and 

 broader, the front margin ciliated, with a long spine at the apex, the hind margin very 

 convex, with three spines on the lower part; the wrist oval, the distal end narrow, the hind 

 margin a little crenate, with nine long plumose spines or setae ; the hand narrow, as long 

 as the wrist, with six slender plumose setee on the hind margin ; the finger straight, not 

 tapering, with a little curved nail, the two together not so long as the adjacent spines, 

 which indeed exceed the length of the hand. 



Second Perseopods. — Side-plates not clearly made out, but apparently much smaller 

 than the preceding pair. Branchial vesicles like the preceding pair. First joint of the 

 limb narrow above, much dilated below, lageniform, with a long apical spine or seta on 

 the hind margin, and a spine above the apex on the front margin ; the second joint short, 

 with an apical seta behind ; the third joint more triangular than in the first perseopods, 

 similarly armed, not nearly so long as the wrist ; the wrist long, oval, much larger than 

 in the first perseopods, attached to the third joint by the top of the smooth front margin, 

 the hind margin from apex to apex set round with twenty-two long plumose setse, those 

 below being the longest ; the hand very much smaller than the wrist, a narrow oval, 

 rather wider at the truncate distal end than at the base, with an apical seta in front, and 

 eight verj'' long ones on the serrate hinder margin ; the finger is small, straight, with a 

 little decurrent tooth or spinule on the inner margin at the base of the short curved nail. 



Third Pereeopods. — The side-plates appear to be small, but the extreme delicacy and 

 transparency of these and the other side-plates make it extremely difficult to ascertain 

 their precise boundaries, and in Dana's figures of this genus they are almost concealed 

 under a blotch of colour.^ The branchial vesicles reach below the second joint of the 

 limb. The first joint is oval, the front longer than the hinder margin, with three seti- 

 form spines at intervals and a small apical spine, the hind margin of great tenuity ; the 



■ By Bovallius, Aniphipoda Synopidea, pp. 9, 10, a clear account is given of the side-plates of Synopm ultramarina, 

 Dana, as follows : — " The epimerals of the first and second segments are as long as the segments, of an irregular shape 

 and only half as deep as long. The epimerals of the third segment (PI. L fig. 13) are enormously developed. They are 

 quadrangular, with the upper corner (the articulation with the segment) truncate, and the hinder margin excavate. At 

 the inside of the upper corner is a tuberculous prominence, against which the upper end of the femur articulates; the 

 epimeral is as deep as the length of the femur of the corresponding leg, quite as large as the femur of the fifth pair. 

 The epimerals of the fourth segment are scarcely as long as the segment (PL L fig. 14), deeper than long, the anterior 

 margin rounded, the posterior straight ; at the middle of the upper margin there is on the inside of the epimeral a 

 tubercular projection for the articulation with the leg. The epimeral reaches as far down as half the length of its femur, 

 and is partly concealed by the femur of the filth pair of pereiopoda. The epimerals of the fifth and sixth segments are 

 longer than the segments, rounded at both ends, more than twice longer than deep ; the posterior portion is a little 

 deeper than the anterior. The last epimerals are shorter than the segment and smaller than the preceding, but of the 

 same form (PI. I. fig. 17)." Of Synopia scheeleana, he says, " The epimerals (PI. II. fig. 22) resemble very closely those 

 of S. ultramarina." 



