862 MRS. E. W. SEXTON ON AMPHIPODA [NoV, 23, 



I have bent the hand back to the level of the other joints, in 

 order to show its true contour. The palm has a submarginal row 

 of small setae on the outer surface, and 2 or 3 clusters of longer 

 setee, and carries besides in all the specimens (male and female) a 

 regular fringe of minute spinules on the margin, extending round 

 the palmar angle. The sensory spines at the angle are notable 

 for the great length of their apical filaments ; the young female 

 has 2 spines on the ou.tside and 3 on the inside of the angle, the 

 larger specimen more. Similar spines occur on the palm of the 

 second gnathopod hand and on the perseopods. The posterior 

 margins of the 5th and 6th joints are deeply inset with clusters 

 of sensory setfe, and the under surfaces of both joints carry two 

 longitudinal rows of groups of these setee. The finger (fig. 14) 

 is broad, curved, and serrated in all the stages, a setule being- 

 inset in each serration ; the number of the serrations increases 

 with age. The tip of the finger fits into a small groove on the 

 inner surface of the palm between the two groups of spines at the 

 angle. 



Male (fig. 9). — The proportions of the 5th and 6th joints differ 

 in the male. The anterior margin of the 5th joint is half as long 

 again as the 6th, instead of only slightly longer as in the female ; 

 and the posterior margin of this joint is convex and not produced 

 to a lobe at the distal angle. The shape of the hand is different 

 in the two sexes, the hind margin being shorter than the palmar 

 margin in the male, longer in the female. The finger also is 

 longer in proportion, with more serrations. 



Second gnatlwpod (figs. 11, 12, & 13) powerfully developed. 

 2nd joint broad and curved, with some of the long delicate setae 

 proximally on either side ; both this and the succeeding joint are 

 prolonged at the anterior angles in large rounded pellucid lobes. 

 The 4tli joint is produced posteriorly to a subacute lobe tipped 

 with sensory setpe ; the 5th is also produced posteriorly, to the 

 same width as the 6th joint, its contour in the female forming 

 one continuous line with the Gth ; posterior margins of both 

 inset with groups of sensory setfe, more in number in the larger 

 specimens. The hand undergoes a i-emarkable amount of modifi- 

 cation with the growth of the animal, especially in the female. 

 Both the hand and the finger differ in the two sexes. 



Female (figs. 11 & 12). — In the immature specimen 3 mm,, 

 the whole of the posterior margin is evenly curved, the palm, 

 defined by 2 sensory spines, being the same length as the hind 

 margin. In the young female 5*5 mm., sexually mature but not 

 full-grown, the posterior margin is still convex, but the palm is 

 half as long again as the hind margin, and the palmar angle is 

 developed ; while in the large female 7*5 mm., the palm is concave 

 instead of convex, with the palmar angle acutely produced, and is 

 more than twice the length of the hind margin . The palmar margin 

 ill the young female projects in a small subacute lobe at about 

 one-third of its length from the finger articulation ; the whole of 

 the margin is crenate ; and the tip of the finger fits into a small 



