1000 THE VOYAGE OF H.M.S. CHALLENGER. 



Synopioides macronyx, n. sp. (PI. XCIVa.). 



Outline of head and back similar to that of Synopia scheeleana except at the fourth 

 segment of the pleon, which appeared to have a laminar triangular process produced 

 backwards on either side of the dorsal line, but these processes were not satisfactorily 

 made out ; the postero-lateral angles of the first three pleon-segments were more or less 

 acute, those of the third segment most so. 



Eyes not perceived. 



Upper Antennse. — The peduncle very short, the first joint scarcely projecting beyond 

 the head, broad, about as long as the other two united, the upper margin longer than the 

 lower ; the second joint abruptly narrower than the first, a little longer than the still 

 narrower third joint ; the flagellum about five times as long as the peduncle, at first 

 very thick, after the first six or seven joints tapering very rapidly to the thirteenth, 

 and then becoming very slender for the remaining joints, which are about twenty in 

 number ; the first joint is as long as the following five or six united, and together with 

 the next eight or nine carries a large brush of broad and long cylinders, as well as 

 slender spines ; some of the remaining joints have small setules ; the secondary flagellum 

 has three joints, together about as long as the first eight of the primary, the first joint 

 considerably longer than the other two united, and much broader, the second longer and 

 broader than the third ; the third linear, tipped with two setae. 



Lower Antennae longer than the upper ; the first joint dilated, second very short, 

 gland-cone small, a little prominent ; the third joint about as long as the two preceding 

 united, broad, with one margin convex, carrying some small spines; the fourth joint long 

 and slender, widest near the base, armed at intervals with spines, some setiform, others 

 stout, these latter being bristly for part of their length, a peculiarity shared by the stout 

 spines in other parts of this animal; the fifth joint elongate, but shorter and thinner than 

 the fourth, with spinules at intervals ; the flagellum longer than the peduncle, consisting 

 of about thirty unequal slender joints, with setules at the apices of most of them. 



Upper Lip. — The distal margin of the principal plate not very broad, flattened, 

 smooth ; the outer plate not reaching nearly so far forward, with the distal margin almost 

 the full breadth of the plate, emarginate but not deeply, smooth. 



Mandibles. — The cutting edge of the left mandible (the right on the Plate) is broad 

 and squared, with a sharp, projecting tooth at the upper end, accompanied by a smaller 

 one above it, not projecting, and a rounded one alongside of it ; at the lower end there is 

 a smaller projecting tooth, with a still smaller below it, less projecting ; the intermediate 

 margin straight, cut into many minute teeth ; the secondary plate is not much less broad, 

 the upper corner rounded, minutely denticulate, the denticulation being continued for 

 some distance along the front margin, and then followed by a row of six stronger teeth, 

 and a seventh much larger and more prominent than the rest ; the cutting edge of the 



