334 MR. F B. BEDDARD ON THE ISOPODA COLLECTED [May 20, 



usually differ in the two sexes, are the same in this species. The males 

 also are larger than the females, the largest male specimen in the 

 ' Challenger ' collection measuring 34 millim. in length and 31 millim. 

 in breadth, while the length of the largest female specimen is only 

 32 millim. in length by 26 millim. in breadth. 



In both sexes the body is roof-shaped, sloping gradually downwards 

 on either side from the median line, which is distinctly keeled ; the 

 posterior margin of each segment has a short tubercle in the median 

 line. The cephalic shield has the same texture as the rest of the 

 bod) r , and hardly projects above the level of the first thoracic 

 segment. The latter is not divided into two portions by a transverse 

 suture ; it is prolonged anteriorly into a short rostrum, and a ridge, 

 which extends on either side from the rostrum to the lateral margins 

 of the shield, divides off the antero-lateral portions as in Serolis 

 bromleyana. The second, third and fourth epimera are separated by 

 a distinct suture from the rest of the segment. 



The caudal shield is irregularly pentagonal in outline ; the pos- 

 terior extremity is slightly turned up ; there is a distinct median 

 carina, which divides into two at the upper end ; on either side of 

 this is another Y-shaped ridge, inclined at a slight angle to the 

 longitudinal axis. 



The second pair of antennae are distinctly longer than the anterior 

 pair. 



This species was dredged at the following stations: — Station 122, 

 400 fathoms ; Station 146, 1375 fathoms ; and Station 147, 1600 

 fathoms. 



The remaining five species form a well-marked group, confined to 

 the shores of Southern and Western Australia. They are to be dis- 

 tinguished by the characters of the fifth and sixth thoracic segments 

 from all the other species of Serolis ; the dorsal portion of the fifth 

 segment is extremely narrow, while the dorsal portion of the sixth 

 segment is either altogether absent or fused with the succeeding 

 first abdominal segment ; with one exception — Serolis minuta, which 

 is a transitional form — the epimera of the abdominal segments are 

 undeveloped and the caudal shield terminates in a slightly bifid tip ; 

 the first thoracic segment is not divided by a suture ; the females 

 also appear to be larger than the males ; the last-mentioned characters 

 however, although common to all the members of this particular 

 group, are also to be found in other species. All these Australian 

 species are small, the largest not measuring more than 20 millim. in 

 length. One species belonging to this group is already known, viz., 

 Serolis tuberculoid, Grube. 



5. Serolis australiensis, n. sp. 



Of this species the 'Challenger' obtained three examples, two males 

 and one female ; both the males are the same size, measuring 1 1 

 millim. in length by 8 millim. in breadth ; the female is rather larger, 

 measuring 13 millim. in length and 11 millim. in breadth. In other 



