1884.] DURING THE VOYAGE OF H.M.S. 'CHALLENGER.' 333 



flattened and not so spine-like as in the last two species ; the sixth 

 pair, as usual, are the longest, and project backwards beyond the 

 caudal shield for a space of about its own length ; the other epimera 

 increase in size from before backwards ; the anterior and posterior 

 processes by which eachepimeron "articulates" with the neighbouring 

 ones are further away from the proximal end of the epimeron, which 

 gives the epimera the appearance of being shorter than they really 

 are ; the fifth and sixth epimera (as well as the three in front) are 

 separated from the tergal portion of the segments by a distinct suture. 

 The epimeron of the first segment shows traces of its original com- 

 position out of two epimera by the presence of a transverse ridge, 

 and another ridge, continuous with that upon the cephalic shield, 

 crosses its anterior half, bending backwards at the margin to join the 

 distal extremity of the first transverse ridge ; the epimeron of the 

 second free abdominal segment projects for a short distance beyond 

 the caudal shield ; the epimeron of the third abdominal segment 

 extends about halfway down the caudal shield. 



The caudal shield is divided into two portions by a sinuate trans- 

 verse ridge ; it is slightly keeled, and near the anterior margin is a 

 short flat spine in the middle line, on either side of which is an 

 obliquely placed ridge running towards the lateral margin of the 

 caudal shield. 



The two pairs of antennae are about equal in length. 



Station 120, 675 fathoms ; off Pernambuco. 



4. SEROLIS ANTARCTICA, n. Sp. 



The three species just described agree with each other, and differ 

 markedly from all the shallow-water species of Serolis by the 

 enormous development of the epimera ; the present species, although 

 an inhabitant of the deep sea, has the general appearance of one of 

 the shallow-water forms. The general form of the body is a broad 

 oval ; the epimera are comparatively short, and do not project back- 

 wards as long spiniform processes. This species is at once recognizable 

 by the strongly marked sculpturing on the upper surface of the 

 carapace, which is different from that of any other Serolis, and by 

 the entire absence of eyes. In the place of the latter are two minute 

 tubercles about 1 millim. in extent, which show no traces whatever 

 of a faceted cornea, and no nervous structures could be detected 

 beneath the tubercle, the cavity of which is occupied simply by a 

 plug of connective tissue. The sculpturing on the dorsal surface, 

 which is more marked upon the epimera, consists of a number of 

 ridges arranged in a reticulate fashion. The form of the body 

 differs in the two sexes : in the male the outline of the body is more 

 circular than in the female ; the breadth of the body in the former 

 is proportionately greater than the length, owing chiefly to the 

 greater length of the epimera. As in all other species of Serolis the 

 sixth epimera are the longest, and extend just beyond the end of the 

 caudal shield in the male ; in the female the terminations of the sixth 

 pair of epimera are just on a level with the end of the caudal shield. 

 The ventral portion of the three free abdominal segments, which 

 Proc. Zool. Soc— 1884, No. XXIII. 23 



