1042 THE VOYAGE OF H.M.S. CHALLENGER. 



portion denticulate ; the peduncles of the third pair much shorter than the rami, apically 

 acute below, with a spine and some spinules on the upper margin; the rami lanceolate, 

 subequal, reaching much beyond the preceding pair, carrying marginal spines of various 

 kinds, some being slender and setiform. 



Telson subequal in length to the peduncles of the third uropods, cleft for three-quarters 

 of its length, the cleft nowhere dehiscent; the outer margins converging little for the first 

 two-thirds of the telson's length, then rapidly ; a feathered cilium and lower down an 

 apically plumose spine or seta are inserted on the margin just before the apex is reached ; 

 the surface on either side has five spines or setules. 



Length. — The specimen, in the position figured, measured, in a straight line from 

 the front of the head to the apex of the third uropods, seventeen-twentieths of an 

 inch. 



Locality. — Station 163b, Port Jackson, June 3, 1874; depth, 35 fathoms; bottom, 

 hard ground; bottom temperature, 63°'0. One specimen, female. 



Remark. — The specific name, derived from the Latin word acinaces, a Persian sabre, 

 refers to the sharp curved dorsal outline of the animal. 



Ampelisca chiltoni, n. sp. (PL CIIL). 



The acuteness of the dorsal compression seems to be limited to the head, which is 

 truncate in front ; the posterior lateral angles of the third pleon-segment produced in a 

 small acute point ; the fourth segment having a small transverse dorsal depression, beyond 

 which the dorsal line is rather sinuous, ending in an angular apex ; the dorsal division 

 between the fifth and sixth segments is very slightly marked ; the dorsal line of the sixth 

 segment divides at about the centre, forming two small wings, the median line convex, 

 the wings straight at the top, ending angularly on each side of the telson, the postero- 

 lateral angles sharply produced at the base of the uropods, and furnished with spines, the 

 lower margins carrying plumose setae. 



Eyes and Antennae nearly as in Ampelisca acinaces. In one specimen examined 

 there were twenty-eight joints on the flagellum of the lower antennae ; the first two joints 

 of the peduncle appeared rather more dilated than in the compared species, the flagellum 

 also being shorter. 



Upper Lip. — The distal margin of the inner plate flatly convex, ciliated, with a faint 

 emargination not central ; the outer plate broader, with an almost semicircular outline, 

 and a faint distal central emargination. 



Mandibles similar to those of Ampelisca acinaces; but the spine-row consists of ten 

 spines ; the molar tubercle has a tooth on the forward side ; the margin of the crown is 

 set with strong denticles in the left mandible on the inner side only, the opposite side 



