68 THE VOYxVGE OF H.M.S. CHALLENGER. 



segment than in the rest. The two last thoracic segments have only one tubercle, on 

 either side, which form the outer extremity of a slight ridge. 



AntenncB. — The first pair of antennae has a stem composed of four joints, of which 

 the thii-d is rather more than twice as long as either of the two basal joints ; the filament 

 consists of some fifty joints ; in the second pair of antennte (PL VI. fig. 2) the third 

 joint has its posterior border prolonged into a spine as figured byGrube;' the upper 

 surface of this and the succeeding joint has a strong longitudinally running ridge ; the 

 upper margin of the fourth and fifth joints, which are as usual the longest, is sinuous, and 

 .a tuft of hairs springs from the summit of each of the elevations ; the filament has about 

 twenty joints. 



In the maxillipedes the stipes is almost triangular in shape ; the lamina is pro- 

 portionately very stout and strong, its diameter being equal to that of the stipes. Just 

 below the articulation of the palp is a curved ridge ; the second joint of the palp, instead 

 of being heart-shaped, has its two sides almost parallel, the curvature of the outer margin 

 following that of the convex inner margin. 



The third pair of thoracic appendages is quite, as described by Grube, but I am 

 inclined to think that both his specimen and mine are immature males {ante, p. 16). 



The ambulatory limbs of this species are characterised by being mainly provided with 

 one kind of spines which are of varying length, but always stout and strong. The end is 

 bent and seems to be of a somewhat softer consistency than the rest. The stout serrated 

 spines, so characteristic of the ambulatory limljs of other species of Serolis, are only 

 present in small numbers in Serolis hiherculata. 



The three abdominal appendages are hardly difi"erent from those of other species ; the 

 basal portion is, however, not prolonged into an angle bearing two or three plumose hairs 

 as in many other species ; in this respect they agree with Serolis australiensis, &c. The 

 exopodite of the first pair of gills is divided into two by a transverse suture, which is at 

 right angles to the long axis. 



Generally speaking, the appendages of Serolis tuherculata are very closely similar to 

 those of the next species to be described. 



A figure of the female is given on PI. VI. fig. 1. 



Station 161, April 1, 1874; off" East Moncoeur Island, Bass Strait; depth, o8 

 fathoms ; bottom, sand. 



Station 162, April 2, 1874 ; off" East Moncoeur Island, Bass Strait; depth, 38 to 40 

 fathoms ; bottom, sand. 



' Loc. cit., 1)1. V. fig. 2. 



