DESCRIPTION OF SPECIES 



337 



Fig. 14. Serolis orbiculata, n.sp., $: x lo. 



rostrum for the reception of the antennules, and behind the rostrum is a low transverse 

 ridge extending to the lateral margins of the head. The eyes, which are oval or slightly 

 reniform in shape and contain black pigment, are situated on raised areas towards the 

 postero-lateral angles of the 

 head; the area between the 

 eyes is hollowed out and the 

 lateral portions of the cepha- 

 losome are smooth. 



The third and fourth (first 

 two free) thoracic somites are 

 sub-equal, the fifth not quite 

 as long, the sixth about half 

 the length of the third; the 

 seventh is fused dorsally with 

 the first abdominal segment 

 for a considerable distance on 

 either side of the middle line. 



The coxal plates are well 

 developed, those of the first 

 three free somites are separ- 

 ated from them by sutures ; those of the seventh somite extend backwards to about the 

 middle of the protopodite of the uropod and just beyond the middle of the terminal 

 segment: those of the male are very slightly longer than those of the female. 



The first three abdominal segments are broad, with a length equal to that of the fifth 

 thoracic somite ; the pleural plates of the second and third segments are short and do 

 not extend beyond the anterior margin of the broad terminal segment. Each of the 

 sternal plates of these segments has the median posterior border produced into a small 

 spine, increasing in length from the first to the third. The terminal segment is triangular 

 in shape, with the angles approximately equal and well rounded, and with the apex 

 directed backwards ; on its dorsal surface is an ill-defined median dorsal carina, on either 

 side of which, placed at some distance from it, is a short lateral carina. This is made 

 more conspicuous by the presence of a line of deeper pigmentation. 



The antennule is less than half the length of the antenna ; it consists of a peduncle of 

 four and a flagellum of eight joints. The first peduncular joint is short ; the second and 

 third are both about twice the length of the first, whilst the fourth is shorter, being only 

 about one-third the length of the third : the second and third joints are sparsely fringed 

 with delicate setae. The flagellum consists of seven joints of about equal length, but 

 narrowing distally, and a very minute terminal joint which bears a single sensory and 

 several simple setae ; a sensory seta is present at the anterior distal angle of all except the 

 first two joints of the flagellum. 



The antenna consists of a peduncle of five and a flagellum of six joints. The first 

 peduncular joint is short, broader than long, with its inner border fringed with short 



