336 DISCOVERY REPORTS 



Beddard, and S. bakeri, Chilton ; the three are together characterized by the facts that 

 (i) the tergum of the seventh thoracic somite is fused with that of the first abdominal 

 segment ; (ii) the coxal plates of the three free somites are separated from them by 

 sutures, and (iii) the coxal plates of the seventh somite are comparatively short. In 

 each species the pleural plates of the third abdominal segment extend back farther 

 than do the coxal plates of the seventh thoracic somite. 



The form of the antennule is the same in the three species ; the second joint of the 

 peduncle is the longest, the penultimate joint of the flagellum very short and the 

 terminal one long and delicate. The form of the modified spines on the inner margin 

 of the propodus of the second thoracic appendage is very much the same in all three 

 species, and in each the setae on the remaining appendages are simple, long and delicate. 



If the size of the specimen of .S. yongei (2-9 mm. long, 2-5 mm. broad) is any indica- 

 tion of that of the adult, this species is considerably smaller than either 5. bakeri or- 

 S. minuta. The main difference appears to lie in the ornamentation ; the dorsal surface 

 of the body of S. yongei is practically smooth and there is only a sHght median dorsal 

 carina on the terminal segment, whereas in S. mimita there are three tubercles on the 

 posterior part of the cephalosome and one in a median position on each of the thoracic 

 and abdominal segments. In S. bakeri the head bears three rounded tubercles on its 

 posterior margin, but these are absent from the thoracic and abdominal segments ; the 

 terminal segment bears a conspicuous median dorsal carina and its posterior extremity 

 is narrow and rounded. 



The three species are all recorded from the Australian coast ; but S. yongei, from the 

 Great Barrier Reef, comes from a locality considerably farther north than the other two. 

 S. bakeri is recorded from Encounter Bay, South Australia, and S. jniniUa from Port 

 Philip, South Australia, and off St Francis Island. 



27. Serolis orbiculata, n.sp. (Figs, i b, e, 14, 15). 



Occurrence. St. WS 222: 48° 23' S, 65° 00' W, 100-106 m.; i ? (non-b.). 

 St. WS 808: 49° 40' 15" 8,65° 42' W, 1 10-107 m.; 1$. 

 St. WS 809: 49° 28' 15" S, 66° 29' W, 107-104 m.; i ? (b.). 

 St. WS 813: 51° 35' 15" 3,67° 16' 15" W, 106-92 m.; i ? (b.). 

 St. WS815: 51° 51' 45" S, 65°44' W, 132-162 m.; 3 ?? (b.), 3 (non-b.), and i <?. 



Description. The body (Fig. 14) is broadly ovate, not much longer than broad; 

 the male is 8-5 mm. in length and 8 mm. in greatest breadth, and the largest female 

 10-5 mm. in length and 9 mm. in greatest breadth. The male, as in so many species of 

 Serolis, is slightly broader in proportion to its length than is the female. 



The surface of the body is smooth, sparsely covered with small microscopic conical- 

 shaped projections. The colour of spirit specimens is brownish towards the centre of 

 the body, paler towards the margins, the whole covered, except for the anterior margins 

 of the somites and their coxal plates, with small spots of black pigment. 



The head is convex dorsally, shield-shaped, broader than long, with its greatest 

 breadth anteriorly. The anterior margin is excavated on either side of a short median 



