_105_ 



pair of legs rather unlike those in female, and much smaller, distal joint narrow 

 oblong in form, with some of the marginal setae spiniform, inner expansion of 

 proximal joint quite short, scarcely extending to the middle o the distal joint, 

 and provided with only 3 marginal setse, the outermost one spiniform. Genital 

 tubercles with 3 subequal setse. 



Body of a golden yellow colour, more or less variegated with a dark 

 reddish brown pigment, especially along the ventral face and at the posterior 

 edges of the segments. 



Length of adult female 1.40 mm., of male 1.20 mm. 



Remarks. This form I regard as the type of the genus Thalestris, in the 

 restriction here adopted. It is one of our larger Harpacticoids, and is moreover 

 easily recognizable by its very robust form and the exceedingly powerfully devel- 

 oped posterior maxillipeds, which somewhat resemble those in Harpacticus chelifer. 



Occurrence. I have found this form not unfrequently in several localities 

 of the west coast of Norway, as far as to the Trondhjem Fjord, in moderate 

 depths among algae. It moves in the usual somewhat jumping manner. When 

 disturbed, it curves its body more or less sharply ventrally, and remains in this 

 attitude quite motionless for some time. 



Distribution. British Isles (Brady), Heligoland (Glaus), coast of France 

 (Canu). 



66. Thalestris gibba (Kr0yer). 



(PI. LXI). 

 Harpacticus gibbus. Kvayer, in "Gaimard" Voyage en Scandinavie. PI. 43, figs. 2. a p. 



Syn: Thalestris polaris, Scott. 



Specific Characters. Female. Body somewhat more slender than in the 

 preceding species, otherwise of a very similar aspect, with the back more or less 

 gibbously curved, and the integuments very thick and tough. Cephalic segment, 

 as in T. longimana, of considerable size and somewhat compressed anteriorly, 

 with the epimeral parts rather deep and curved in the middle ; rostral projection 

 more prominent than in that species, and acutangular at the tip. Posterior edges 

 of all the segments minutely crenulated. Urosome considerably exceeding half 

 the length of the anterior division, and having the segments very sharply defined, 

 the genital one of moderate size and less expanded than in T. longimana: last 

 segment very small. Caudal rami unusually produced, being nearly 3 times as 

 long as they are broad, apical setae, on the other hand, much shorter than in 



14 Crustacea. 



