ENTOMOSTRACA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 317 



Genus Phyllopodopsyllus, Scott, 1896. 



Phyllopodopsyllus mossmani, new species. (PI. V. figs. 1-14.) 



Female. In its general appearance, the female of this species resembles that of 

 Plujllopodopsyllus bradyi ; there are, however, a few small but obvious differences 

 which, though they may not be of so much importance as to separate this form 

 generically, are yet sufficient to exclude it from any species hitherto described. The 

 length of the specimen represented by the drawing on PL V. is 071 mm. 



Antennules nine-jointed, like those of the type species ; the first joint is large and 

 about equal to the combined lengths of the next three joints : these three joints do not 

 differ much in size, but the third and fourth are each rather smaller than the preceding 

 joint ; the seventh and eighth are smaller than any of the others, and are together only 

 equal to about half the length of the end joint ; the second joint wants the spur-like 

 process with which that joint is armed in both the type species : Phyllopodopsyllus 

 bradyi and the Phyllopodopsyllus furcifer described by G. 0. SARS (fig. 2). The 

 antennae are similar to those of the type species, as are also the maxillae, but the 

 mandibles are rather stouter, and the two branches of the mandible-palp do not differ 

 so much in length, the lower branch being in the type species distinctly smaller than 

 the other. The two pairs of maxillipeds are similar to those in the type species (fig. 4). 



The swimming legs have the inner rami all two-jointed and the outer rami three- 

 jointed ; in the first pair the inner ramus is fully one and a half times longer than 

 the outer one, the first joint being considerably longer than the entire outer ramus ; 

 the end joint, which is much smaller than the first, is armed with a stout apical claw 

 and an elongated seta. In the second and third pairs, the inner ramus, which scarcely 

 reaches the end of die second joint of the outer, has the joints subequal. In the fourth 

 pair, the inner ramus is very small, being shorter than the first joint of the outer one 

 (see figs. 7-10). 



The fifth pair form each a large foliaceous plate, somewhat oval in outline ; its length 

 is equal to about twice the width, its distal end is rounded but the inner portion 

 slightly produced, and it is furnished with several small setse round the inner margin 

 and apex (fig. 11). 



The caudal rami are about equal in length to the last segment of the abdomen, and 

 the principal tail seta, which is somewhat dilated at the base, is long and slender. 



Male. The male is smaller than the female, and measures only about 0'55 mm. in 

 length. The structure of the antennules is modified so that they form effective grasp- 

 ing organs. In the second pair of swimming feet the inner rami are proportionally 

 rather longer than in the female. 



The fifth pair are small and normal in structure (fig. 12). The caudal rami are 

 more slender than in the female, and the principal tail seta is not only elongated but 

 is also somewhat stout and spiniform. 



With these exceptions, the structure of the male and female is somewhat similar. 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 563.) 



