124 PERCY SLA DEN TRUST EXPEDITION 



Inner uropod (fig. 5) slightly longer than the outer, its inner margin armed with 

 a row of spines, arranged more or less in groups and extending to the apex. 



Outer uivpod (fig. 5) with the terminal joint about one-fourth of the length of the 

 proximal joint and about one and a half times as long as broad ; outer margin of the 

 proximal joint armed with seven spines which occupy considerably more than one-half 

 of the margin, the proximal four very distantly placed, the terminal three situated at 

 the junction with the terminal joint. 



Length of male specimens, not quite mature, 6 mm. 



Figs. 2, 3 and 4 on Plate 6 show the endopods of the second, third and fourth 

 thoracic limbs magnified to the same scale and sufiiciently explain these appendages. 



The genus Hemisiriella was founded by Hansen for two species which differ from 

 Siriella in the following points : — 



(1) In having the carapace unusually short so that it leaves fully exposed, both 

 laterally and dorsally, the last two segments of the thorax. 



(2) In the comparative greater length of the third joint of the antennular peduncle. 



(3) The small size of the antennal scale. 



(4) In several small details in the structure of the mandibles. 



(5) In having the third pair of thoracic limbs (first pair of thoracic legs according 

 to the terminology adopted by Hansen, the first and second pair of thoracic limbs being 

 called by that author maxillipede and gnathopod respectively) greatly elongated, with 

 the dactylus very rudimentary and hidden in a brush of peculiar setae. 



It is with very great diffidence that I refer the present species to the same genus, for 

 it agrees with Hemisiriella in only two of the above five points, viz. in the small size of 

 the antennal scale and in the form of the mandibles. 



As regards the last of the five points already mentioned, H. gardineri shows a 

 remarkable feature. It has one of the thoracic limbs considerably elongated and exhibit- 

 ing the same structure as in H. parva and H. pidchra but, instead of it being the third 

 thoracic limb as in the latter two species, it is the fourth thoracic limb of H. gardinei^ 

 which is thus elongated. I have been led to refer H. gardwieri to the genus Hemisiriella 

 mainly on its possession of an elongate thoracic limb, agreeing in its essential structure 

 with those described for the genus though differing in position. It is quite probable that 

 future observers may regard the difference in position of the elongate limb as of generic 

 unportance for it would appear to be an exactly parallel instance to that seen in the 

 genera Nematoscelis and Nematohrachion among the Euphausiacea. Attention may be 

 directed to Caiman's remarks on the latter genera (Caiman, 1905). 



For the rest, H. gardinei'i resembles a true Siriella in the form of the carapace, 

 antennular peduncle and telson. The species is sufficiently distinguished by the com- 

 bination of characters presented by the uropods, antennal scale and thoracic limbs. 



