ANNALS OF SCOTTISH NATURAL HISTORY 228 
IDYA MINOR, sf. z., Plate IV. Figs. 11-17. 
Description of the Female—Length .7 mm. (5 of an 
inch). Body closely resembling /dya 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 11 
Numbers of the joints [tink ay RN RI RAG els 
The first three joints of the secondary branches of the 
antennz are short; the fourth joint is as long as the 
second and third together (Fig. 13). Mouth organs some- 
what similar to those of /dya furcata. The first pair of 
swimming feet are robust; their outer branches do not reach 
mucin 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 /dya furcata. In the fifth pair the inner 
portion of the basal joint is subtriangular in outline and 
bears three setz 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 setze, both surfaces of the secondary joint are covered 
with minute hairs. Caudal stylets short. Ovisac large. 
Hatitat.—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 antennz, 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 /dya minor resembles Jdya furcata more 
closely than any of the other described forms; but in the 
latter species the third joint of the antennules is distinctly 
