REPORT ON THE PHYLLOCARIDA. 13 



to structure, the carapace is rather thin and pellucid and very flexible, not at all cal- 

 careous, and without any trace of external sculpturing. It is composed of two distinct 

 layers, an outer chitinous coat, and a soft membrane lining the inside of the carapace. 

 Between the two layers there is a system of hollow spaces anastomosing with each other, 

 and forming together a complicated network of canals, in which the blood circulates. 



The eyes (PI. I. fig, 1, ; fig. 3) are movably articulated to a short segment, lying in 

 front of the antennal segment, and are partly covered by the rostral plate, projecting 

 obliquely at each side (see PL II. fig. 1). They are rather large, nearly as long as the 

 rostral plate, slightly curved, and somewhat tapering, and not as in Nebalia, expanded 

 at the end. The upper edge is slightly convex and densely denticulate, the denticles 

 increasing somewhat in size toward the tip of the eye ; the lower edge is almost straight 

 and quite smooth. The eye-pigment is black, and does not completely fill up the outer 

 part of the eye, forming a narrow, oblong central mass, from which the small, rounded 

 crystalline cones project all around. There is no distinct facetted cornea similar to that 

 found in higher Crustacea. 



The antennulse (PL I. figs. 1. a 1 ; fig. 4) are rather powerful organs, almost pediform in 

 character, and more or less projecting in front of the carapace, immediately below the 

 eyes. They consist each of a strong, four-jointed peduncle, geniculate at the middle, 

 and two terminal appendages movably articulated to the same. The first joint of the 

 peduncle is rather firmly connected with the antennal segment and of a nearly quadrate 

 form, without any spines or bristles. The second joint is almost twice as long, and rather 

 movably articulated to the first, forming with it a more or less distinct elbow-shaped 

 flexure. It is slightly dilated towards the end, which exhibits on the upper side an 

 obtuse projection, at the base of which several slender bristles are affixed ; from the lower 

 side, close to the end of the joint, moreover, four rather strong and recurved ciliated setae 

 arise. The third joint is somewhat shorter than the second, constricted at the base, and 

 likewise very movably articulated, so as generally to form with the preceding joint a 

 strong geniculate bend. At some distance from the extremity there is a slight promin- 

 ence, and between this prominence and the terminal edge a great number of slender, 

 diverging bristles occur. The fourth joint is much shorter, and has only a very restricted 

 mobility in relation to the preceding joint. It is produced along the anterior side to a 

 compressed lanceolate expansion (fig. 6) freely projecting from its end, and strongly 

 serrate along the outer edge. The serrations, from twelve to fourteen in number, are 

 pretty regular, and increase in size toward the tip of the expansion, each of them being 

 finely denticulate at the upper edge. At the base of this expansion a few slender bristles 

 are affixed to the inner surface of the joint. Of the two terminal appendages, the outer 

 one has the form of an oblong-oval lamella clothed along the anterior side and apex with 

 a great number of unequal-sized slender bristles, forming together a dense brush. The 

 inner appendage, representing the true flagellum, is more cylindrical in form, and also 



