ISOPODA OF THE 'LIGHTNING' AND OTHER EXPEDITIONS. 117 



The first gnathopods (iii. gn^) are compact, with a certain uniform squareness about 

 all the joints ; the basos, meros, and carpus are subequal in length ; the two latter lie 

 closely side by side ; the hand carries a thick short finger clasping closely down upon a 

 thick short thumb ; both end in stumpy horn-coloured nails. 



The following six pairs of legs are very slender and small, divided, as in other 

 Tanaidae, into two sets of three. In the first set (iii. c/n^) the basos is rather longer, 

 in the second (in. j^^'P'^) it is distally rather thicker. In all of them the ischium is veiy 

 small, the meros and carpus about equal in length ; the propodos thinner and longer 

 than either, with finely pointed curved fingers. At the distal end of the hand there is 

 a curious short serrate spine above the convex upperside of the finger. 



The uropoda (in. pi. and in. pi.*) are very short, and consist of a short thick 

 peduncle with a two-jointed inner ramus diminishing in thickness distally but not to a 

 fine point ; the first joint is about the same length as the peduncle, the second 

 shorter, terminating in four long divergent hairs ; the outer ramus is uniarticulate, 

 rather longer than the first joint of the inner ramus and terminating in one or two 

 hairs. 



Length 4 millim. 



A single specimen was dredged in the 'Porcupine' expedition of 1869, midway 

 between Ireland and Eockall, in 1-380 fathoms. (Station 30, lat. 56° 24' N., long. 

 ir 49' W.) 



The foregoing description was written years ago, long before the publication of Prof. 

 G. O. Sars's monograph. The genus which we had described for it is undoubtedly the 

 same as Strongylura, to which therefore we assign it, and it is not improbable that our 

 S. arctopliylax may ultimately prove to be the same as the typical S. cylindrata ; but 

 apparently that species is of more elongate and drawn-out form : " Corpus gracile, plus 

 8-ies longius quam latius. . . . Corpus posticum tertiam corporis longitudinis partem 

 nonnihil superans, segmento terminali antecedentibus 4 junctis longitudine sequali." 

 We therefore deem it better to retain the name we had proposed, as further comparison 

 may show other distinctive features ; moreover, there are apparently differences in the 

 antennae, and the outer branch of the uropods, though consisting of only a single 

 joint, could scarcely, we think, have been designated by Prof. Sars as tuberculiform. 

 Strongylura cylindrata was taken on the coast of West Norway. 



Genus 3. Tajs'aella, n. g. 



Animal elongated, subcylindrical, nearly parallel-sided ; integument very hard, polished 

 and shining. Carapace moderately large, constricted slightly in the middle, widening 

 again forwards, slightly rostrate ; no distinct ocular lobes. Pleon subequal to last three 

 segments of perseon, perfectly cylindrical, smooth, composed of six evenly arched 

 segments ; the telson equal to at least four in length, cupuliform. 



VOL. XII. — PART IV. No. 6. — October, 1886. t 



