On a neio Species- of the Isopod Genus Serolis. 209 



XXXVI. — A neic Species of the Isopod Genus Serolis. 

 By W. T. Calman, D.Sc. 



(Published by permission of the Trustees of the British Museum.) 



Among the numerous species of tlie genus Serolis, S. latifrons, 

 Miers, stands apart on account ol: the structure of the uropods, 

 which, as Beddard * pointed out, " recalls that cliaracteristic 

 of the SpliasromidtTC." Beddard also stated tiiat the species 

 differed from all tlie other members of the genus in having 

 minute "epimera^' separated by suture from the first abdo- 

 minal somite. It will be shown below, however, that these 

 structures really belong to the last thoracic somite, of which 

 no trace persists on tlie dorsal surface in any otiier species. 



The Museum lias recently received from the South Shetland 

 Islands specimens of a new species agreeing in these and 

 other characters with S. latifrons. The two species might 

 very well be treated as forming a distinct genus, but it is not 

 convenient to do so without undertaking the re-grou))ing of 

 the remaining species of the genus Serolis. As a contribution 

 towards this re-grouping, the following arrangement, based on 

 some of the more obvious characters, is suggested : — 



A. Uropods without endopod, exopod articu- 



lated to outer margiu of the prolonged 

 spiniform peduncle. Tergum of last tho- 

 racic somite interrupted in the middle, 

 where the first abdominal comes in contact 

 with the penultimate thoracic tergum ; 

 lateral portions persisting as a pair of 

 minute sclerites each with a coxal plate 

 separated by suture Group of S. latifrons. 



B. Uropods with endopod and exopod movably 



articulated with the peduncle. Tergum 

 and coxal plates of last thoracic somite 

 absent. 



a. Tergum of penultimate thoracic somite 



complete Group of S, 2)aradoxa. 



b. Tergum of penultimate thoracic somite 



interrupted in the middle, so that the 

 iirst abdominal comes in contact with 

 the antepenultiuiate thoracic tergum . . Group of S.tiihcrculata, 



The first of these groups will contain, in addition to 

 S. latifrons, only the new species described l)elou\ The 

 group of ^S'. tuhercnlata comprises the six Australian species 



* Rep. Tsopoda ' Challenger,' pt. 1, 1884, p. 4(i. 



