of the Fishery Board for Scotland. 



171 



springs from the distal half of the outer edge of the second joint ; the 

 outer branch is also armed with three stout and two very small spines, 

 there is also a small subterminal and spiniform seta on the inner aspect ; 

 first joint of the inner branches nearly as long as the first joint of the 

 outer branches, both margins fringed with short hairs, while a short 

 plumose seta springs from near the distal end of the inner margin ; other 

 joints very short (fig. 9). The fifth pair has the basal joint broadly 

 foliaceous and shortly produced interiorly, and furnished with four plumose 

 setae on the broadly rounded apex, the second seta from the outside being 

 much longer than the others, while the innermost is the shortest ; secondary 

 joint subcylindrical, about twice as long as broad, and provided with five 

 apical setae, the two inner setae being rather longer than the others and 

 plumose; both margins of the secondary joint are ciliated (fig. 11). Caudal 

 stylets very short (fig. 12). 



Habitat. — Old quarry near Granton, into which the sea ebbs and flows. 



Remarks. — This somewhat critical species may be distinguished from 

 other species of Harpacticus by the structure of the antennules, by the 

 form and armature of the posterior foot-jaws, the length of the first and 

 second joints of the outer branches of the first pair of swimming feet, and 

 by the form of the fifth pair. In all these characters it appears to be 

 intermediate between Harpacticus fulvus and Harpacticus flexus. 



Genus Idya, Philippi (1843). 



Idya gracilis, n. sp. (PI. IV. figs. 13-21). 



Description of the species. — Female, length 1*4 mm. (y 1 ^ of an inch). 

 Body, seen from above, narrow and tapering gently towards the posterior 

 end, length about three and a half times the breadth at the widest part, 

 rostrum small (fig. 13). Antennules scarcely reaching to the end of the 

 first cephalo-thoracic segment, eight-jointed ; the second joint is rather 

 more elongate than any of the others ; the length of the fourth and the 

 last is nearly equal, while the fifth, sixth and seventh are small, as shown 

 by the formula — 



Proportional lengths of the joints, 15 ' 26 • 22 • 18 • 5 • 7 • 4 • 16 

 Numbers of the joints, 1' 2' 3' 4 * 5 ' 6 ' 7 ' 8 



Antennae slender, moderately elongate; secondary branches short, four 

 jointed, furnished with several short plumose setae ; second and third joints 

 subequal and smaller than the others, first and fourth also subequal (fig. 

 15). Mandible rather slender, and the one-jointed branches of the palp 

 are so arranged that there is a considerable distance between them (fig. 16). 

 The basal joint of the anterior foot-jaw is dilated ; the end joint is long 

 and very slender, and furnished near the middle of the posterior margin 

 with two setae — the one plain and slender, the other spiniform and plumose 

 (fig. 17). Posterior foot-jaw large ; two small setae spring from the inner 

 distal angle of the first joint ; the terminal claw is stout and elongate, and 

 has a moderately long plumose setae alongside of it interiorly ; both the 

 first and second joints are also provided with a few small marginal hairs, 

 as shown by the drawing (fig. 18). The inner branches of the first pair 

 of swimming feet are of considerable length and very slender ; the second 

 joint, which is nearly one and a half times longer than the first, is equal 

 in length to about seven times the width at the broadest part ; a plumose 

 seta, extending to slightly beyond the end of the branch, springs from the 

 lower half of the inner margin of the first joint ; and a small seta, also 



