18 W. M. TATTERSALL. 



preanal spine well developed, provided with an external strong tooth and a comb-like 

 row of finer teeth up to twelve in number. 



Antennular peduncle (Fig. 2) rather long and slender, considerably longer than half 

 the carapace ; basal joint rather flattened, considerably wider than the remaining two 

 joints, bearing on its outer distal corner a rather long and slender spine, its anterior 

 margin somewhat overlapping the basal part of the second joint, fringed with 

 numerous setae and exhibiting near the inner side a shallow fissure : terminal two 

 joints very long and slender, subequal in length, their combined lengths slightly 

 exceeding that of the basal joint. 



Antennal peduncle (Fig. 3) very long and slender, nearly as long as the scale, 

 third joint less than half as long as the second. 



Antennal scale (Fig. 3) extending to about midway along the terminal joint of 

 the antennular peduncle, almost five times as long as broad, outer margin terminating 

 in a well-marked spine, inner margin sloping away obliquely towards the apex ; spine 

 on the basal joint moderately long, slender and smooth. 



Mouth parts (Figs. 4-6) do not offer any marked differences from those of 

 Thysanoessa gregaria as figured by Sars (1885, PL XXII). 



Second thoracic limbs (Fig. 8), with the endopod remarkably long and well 

 developed, in full-grown specimens equalling nearly three-quarters of the total length of 

 the body from the eyes to the telson ; meral joint the longest, extending beyond the 

 tip of the antennular peduncle ; carpal joint a little shorter than the meral and more 

 slender, nearly four times the length of the propodal joint, armed with four slender 

 spiniform setse on the outer margin at the distal extremity, and five similar setae on 

 the inner distal margin ; propodal joint with five long spiniform setae on the outer 

 and six on the inner margin ; terminal joint small, tipped with six spiniform setae. 



The remaining thoracic limbs (figs. 7, 9, 10) not differing greatly from the same 

 limbs in T. gregaria. 



Copulatory apparatus (Fig. 11) on the first pleopod of the male exhibits a 

 structure very similar to that figured by Sars for T. gregaria, except that the distal 

 extremities of the two movable processes on the inner lobe do not seem to be serrate. 



Telson slender, apex acutely produced and smooth ; sub-apical spines smooth ; 

 dorsal denticles two pairs, the first pair just anterior to the centre of the telson, the 

 second pair a little anterior to the insertion of the sub-apical spines. 



Uropods exceedingly slender, inner one reaching the apex of the telson, outer 

 slightly shorter. 



Length of the largest specimen, 28 mm. 



I have thought it well to describe and re-figure this species, since Sars' original 

 description was taken from admittedly young forms, and I cannot find that mature 

 specimens have ever been described and figured. • The changes that take place 

 during growth affect principally the rostrum, the second thoracic (or elongate) limb 

 and the preanal spine. 



