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



shield ; the outer margins of the epimera iu all the segments are smooth, without 

 serrations or hairs. On either side of the male generative pores is a slit-like orifice as 

 in Serolis pallida, &c. 



Abdomen. — The second and third segments are provided with epimera which extend 

 farther than the epimera of the sixth thoracic ; those of the third segment reach nearl)^ 

 as far as the middle of the caudal shield. The ventral portion of the three anterior 

 abdominal segments is shown on PL VII. fig. 2', together with the appendages belonging 

 to them ; they are oblong in shape, and each overlaps the succeeding one ; the posterior 

 margin of the first is almost straight, in the others slightly convex. 



The caudal shield is almost triangular in shape, and ends in a blunt prolongation ; 

 the upper surface slopes gently downward on either side from the central keel ; the 

 lateral margins commencing from the attachment of the terminal appendages curve 

 inwards and then slightly outwards, becoming almost parallel just before their termination. 



Antennce. — One of the antennae of the first pair is figured on PI. VII. fig. 4 ; it 

 consists as usual of four joints and a terminal filament ; the proximal joint is round and 

 entirely free from hairs ; the second joint is the largest, its lower surface is furnished with 

 a row of short hairs which are continued on to the succeeding joint ; the third joint is 

 smaller than the second, and the fourth is still smaller. The filament is made 

 up of ten joints, of which the first eight are subequal ; the penultimate joint is very 

 small, and the last slender and elongated. The second pair of antennae (PI. VII. fig. 5) 

 are about one-third longer than the anterior pair ; the basal portion consists of five joints, 

 of which the last is the longest ; the three last joints are furnished with bundles of hairs 

 arranged irregularly over the lower surface. The filament is made up of ten joints, and 

 is almost exactly of the same length as the filament of the anterior antennse, which is an 

 unusual circumstance. 



The mandibles present the usual form, and terminate in a Ijlunt masticatory edge. 



Thoracic Appendages. — The large prehensile organs which form the second pair of 

 thoracic appendages are in general form entirely similar to those of other species, but the 

 spines developed upon the inner margin are as usual distinctive ; several of these are 

 shown in PI. VII. fig. 7. 



The third pair are modified into a prehensile organ which presents some peculiarities 

 distinguishing it from the same appendage in other species of Serolis. Fig. 3 represents 

 the last three joints of the right hand appendage viewed in profile and from beneath. 



The terminal joint is furnished with a remarkable tongue-shaped process arising from 

 the inner side close to the distal end ; along this runs a median crest like the micbib of 

 a leaf. The penultimate joint has five pairs of conical bent spines which are almost 

 exactly similar in shape to those of Serolis convexa. The fourth joint has a bundle of 

 fine closely-set long hairs on its inner surface, as is the case iu Serolis necerxt ; the third 

 joint has several smaller bundles of precisely similar hairs separated by intervals from each 



