228 ANNALS OF SCOTTISH NATURAL HISTORY 



IDYA MINOR, sp. n., Plate IV. Figs. 11-17. 



Description of the Female. Length ./ mm. (-^g- of an 

 inch). Body closely resembling Idya furcata (Baird) in 

 general appearance. Antennules eight-jointed, stout; second 

 and third joints of about equal length, and longer than any 

 of the others ; the first, fourth, and last are also moderately 

 elongate, and nearly equal in length. The formula shows 

 approximately the proportional lengths of all the joints : 



Proportional lengths of the joints 12 18 18 12 3 5 3 n 

 Numbers of the joints i 2345678' 



The first three joints of the secondary branches of the 

 antennae are short ; the fourth joint is as long as the 

 second and third together (Fig. 13). Mouth organs some- 

 what similar to those of Idya furcata. The first pair of 

 swimming feet are robust; their outer branches do not reach 

 much beyond the end of the first joint of the inner 

 branches ; the spine on the exterior distal angle of the first 

 joint of the outer branches scarcely extends beyond the 

 terminal joint (Fig. 15). The second, third, and fourth pairs 

 resemble those of Idya furcata. In the fifth pair the inner 

 portion of the basal joint is subtriangular in outline and 

 bears three setse at the bluntly rounded apex, the middle 

 seta being much longer than the other two ; the secondary 

 joint is somewhat spatulate, the width being greater towards 

 the distal end, the length of the joint is equal to about three 

 times its width, the end is truncate and furnished with five 

 apical setse, both surfaces of the secondary joint are covered 

 with minute hairs. Caudal stylets short. Ovisac large. 



Habitat. In a few localities in Loch Fyne,especially where 

 the water is shallow with a muddy bottom as in Loch Gair and 

 in the vicinity of Carndow and Largabruach ; not uncommon. 



Remarks. Idya minor is the smallest member of the 

 genus that we have yet observed. It may be distinguished 

 by the structure of the antennules and antennae, by the 

 robust form of the first pair of feet and the comparatively 

 broad and spatulate secondary branches of the fifth pair. In 

 general appearance Idya minor resembles Idya furcata more 

 closely than any of the other described forms ; but in the 

 latter species the third joint of the antennules is distinctly 



