300 Dr. W. T. Caiman on a new 



named by Beddard (J. c. pp. GG and 81) as forming- " a well- 

 marked subdivision of the genus," together with S. baJceri, 

 recently described by Chilton *. The group of S. parado.ra 

 includes all the remaining species of the genus, and will no 

 doubt be found to deserve further subdivision. 



Studer f, who describes the uropods of S. latifrons in 

 detail, regards the distal portion of the appendage as corre- 

 sponding to the acute prolongation of the peduncle in S. para- 

 doxa and other species, and states that one of the rami is 

 suppressed while the other is reduced and spiniform. This 

 interpretation (with the added assumption that the persisting- 

 ramus is the exopodite) is adopted here in preference to that 

 of Beddard, who states that " the endopodite becomes fused 

 witli the protopodite and is extraordinarily elongated." 



Beddard states that in S. latifrons "the first abdominal 

 segment, which in no other species of Serolis known to me 

 lias any trace of epimera, has distinct though very minute 

 epimera separated from the tergum by a suture which is 

 continuous with that dividing the epimeron and tergum of the 

 segment in front." The existence of distinct " epimera " (or 

 coxal plates) on an abdominal somite would be without 

 parallel not only in the genus Serolis, but among the Isopoda 

 as a whole. As a matter of fact, the parts in question are 

 quite similar in S. latifrons to those of the new species here 

 described (text-fig. 2). A small sclerite (b), rounded or 

 triangular in form, lies in contact with the external angle of 

 the tergum of the first abdominal somite on each side. 

 Separated from this sclerite by a groove or suture is a nar- 

 rowly triangular or almost linear piece (a) Wedged in between 

 the terga of the first abdominal and the seventh (penultimate) 

 thoracic somites. On disarticulating a specimen these two 

 sclerites are easily separated from the first abdominal somite, 

 and they are then seen to be continuous below with the sternal 

 piece which carries the socket for the last pair of legs. There 

 can be no doubt that the outer of the two sclerites (b) is the 

 coxal plate of the last thoracic somite, and that the narrow 

 piece (a) with which it is connected on the inner side is a 

 vestige of the tergum of the same somite. This persistence 

 of the lateral portions of the tergum is an interesting parallel 

 to what happens in the case of the seventh (penultimate) 

 thoracic tergum in the species of the tuberculata group, 

 although in that case the lateral portions and their associated 

 coxal plates remain of large size. 



* Trans. Roy. Soc. S. Australia, xli. 1917, p. 398. 

 f Arch. Naturg-. xlv. (1) 1879, p. 31. 



