REPORT ON THE AMPHIPODA. 1047 



Ampelisca abyssicola, n. sp. (PI. CIV.). 



The back of the perseon and first three pleon-segments rounded, the head dorsally 

 compressed, in front a little eniarginate at the top, so that the lower part forms a 

 slightly prominent lobe of irregular outline on either side, sloping backwards below ; 

 the postero-lateral angles of the first two pleon-segments rounded, of the third not 

 rounded, but not produced or upturned ; the fourth segment carinate, the carina 

 interrupted by a transverse dorsal depression, and having a small tooth almost at the 

 distal end ; the fifth and sixth segments coalesced, the dorsal point of division depressed, 

 very faintly marked, the segments slightly carinate, the after part of the sixth segment 

 forming a free angle on each side of the central dorsal line, which has a pair of setules ; 

 the posterolateral angles are sharply produced. 



No Eyes of the character usual in the genus Ampelisca could be discovered. 



Upper Antennse not nearly reaching the end of the peduncle of the lower ; the first 

 joint moderately thick, with setules along the central part of both margins, and some 

 slender spines near the narrowed apex; the second joint longer and thinner than the 

 first, not so long as the head, with thin spines chiefly along the lower margin ; the third 

 joint rather more than a quarter the length of the second, quite distinct from the 

 flagellum, with spines at two or three points of the lower margin; the flagellum shorter 

 than the peduncle, with ten joints in one antenna, eleven in the other, the joints slender, 

 all but the last widening a little distally and armed with spines longer than themselves, 

 the terminal joint with three not longer than itself. 



Lower Antennse. — The first two joints very short, the second with a small lobe on 

 the side not pointing forwards, its distal margin produced into two points, one of which 

 is very acute ; the third joint as long as the two preceding united, with one margin 

 straight, the other convex ; the fourth joint long and narrow, with a few spinules on the 

 lower margin and the surface ; the fifth joint rather longer, with a slight curve, similarly 

 armed ; the flagellum slender, with fifteen joints remaining, which are tipped with spines, 

 those on the second, fourth, sixth, ninth, twelfth, and fifteenth being long ones. 



Upper Lip. — The inner plate projecting, rather strongly ciliated near the rounded 

 corners of the distal margin, which centrally is almost straight ; the outer plate is much 

 wider, transversely oval, with the distal margin flattened, straight, and smooth. 



Mandibles.— All the cutting plates strong except the secondary plate on the right 

 mandible, of which the teeth are sharp and almost spine-like ; the outer plates have 

 four or five strong teeth apiece ; in the spine-row there are on the left mandible eight 

 strongly denticulate backward-curved spines ; on the right mandible there are nine, 

 rather longer and less curved ; the molar tubercle is strong, with an irregularly shaped 

 crown set with Uttle teeth ; the palp is strong, with a rather short first joint set as usual 

 low down on the outer side of a high, broad, somewhat folded process which looks like a 



