ISOPODA OP THE ' LIGHTNING ' AND OTHER EXPEDITIONS. 115 



ably longer than the extended wrist upon which it doubles back, the sinuosities of the 

 meeting margins of the two to some extent corresponding. The wrist is ciliated on the 

 upper margin, the hand finely serrated along the greater part of the curved margin 

 which precedes the articulation of the finger ; both thumb and finger have horn-colonred 

 overlapping nails, but when the finger is closed there is still a large gap left between 

 the greater extent of the inner margins ; from that of the thumb there arises a small 

 tooth, and then, nearer to the nail, a larger one with two cilia springing from its side ; 

 the finger is furnished with a small tooth nearly opposite to this one, and another nearer 

 to its own base, so that the two teeth on the thumb are opposed to the cavity between 

 the two teeth of the finger. 



The second gnathopods and first and second perseopods are, as usual in this group, 

 as nearly as possible alike to each other ; it may be noticed, however, that in the second 

 gnathopod (n. gn 2 ) the basos is rather more curved, the bulky basos of the preceding 

 gnathopod almost necessitating this differentiation. In the present species the basos is 

 long and slender, the ischium minute, the meros much like the basos, but only half the 

 length or less ; the carpus still shorter, with two rows of spines in front diverging 

 towards the distal end ; the hand narrow, equal in length to the wrist, and similarly 

 ornamented ; the finger sharp, a little curved, not so long as the hand ; two or three 

 quite simple spines spring from the end of the hand, and are as long as the finger. In 

 the three posterior perseopods (n. prp 5 ) the meros is shorter, wider at the middle than 

 at the base, and slightly decurrent, the slender curved finger with its fine sharp nail is 

 even longer than the hand, and the spines at the end of the hand are short and flat- 

 tened and simple, not one third as long as the fingers ; none of the spines of the 

 perseopods in this species are either serrulate, dentate, or covered with prickles. 



The pleopods (n. pip) have very long and densely plumose seta?. 



The uropods (n. urp), on a moderately stout peduncle, carry a long multiarticulate 

 inner ramus and a short two-jointed outer one. Of the two minute joints of which the 

 shorter ramus consists the second is twice as large as the first, but the total length 

 scarcely exceeds that of the first articulation of the longer ramus ; the latter is imper- 

 fect, but six articulations remain. 



All along the back of the animal, from head to telson, minute upright hairs are 

 visible. 



Length 5 - 5 millim. 



A single specimen, an adult male, was taken in the ' Porcupine ' Expedition, 1809, 

 Station 1, lat. 51° 51' N., long. 11° 50' W., in 370 fathoms— that is, off Valentia, in the 

 south-west of Ireland. 



