COPEPODA. 19 



In tlie fourth pair the ^('3 is not three times as h^ng as broad (IG : G). The 

 anterior antennaj are a little longer than the cephalothorax. 



The 6 is a little smaller than the 9 , and presents the same sexual diftereuces as 

 in other Euchaetae. The bunches of hairs on the last thoracic segment, so prominent in 

 the ? , are absent in the i . 



The first feet have a three-jointed exopodite, the outer margin of which is not so 

 concavo-convex as in the 9 , and its Se are short. 



In the second pair, the Se of the exopodite are also smaller, the Se of Re 2 only 

 reacliing the origin of the Se 1 of Re 3 ; the Se 2 of Re 3 being little more than half 

 the length of the distal part of the segment. The fifth feet are characteristic. The 

 penultimate segment of the left foot is prolonged on the upper margin into a strongly 

 toothed process, and has a setose conical uuhaired process on the distal margin, the 

 last segment into a long process, narrow and with a strong bunch of hairs at the distal 

 extremity, and with a large conical and strongly haired pror;ess. (This process is 

 sometimes nearly as long as the principal process of the penultimate joint.) 



The first basal is short, the second l)asal long, and with very small and rudimentary 

 cudopodite. 



The right foot has short first basal, very broad serond l)asal, long first and second 

 Re (which are coalesced), and with the last segment blunt and lounded. 



EUCHAKTA SIMILIS. 



(Plate IV., figs. 1, 2, 3, 4.) 



This species occurs plentifully in the same samples in which E. antarctica is 

 present. For a long time I regarded them as merely different stages in the history of 

 the same animal, but the careful examination of a great number of individuals from 

 different tow-nettings proves the constancy of the points of difterence between the two, 

 and as many of the E. anfarctica and E. «iinilis have spermatophores or egg sacs 

 attached, I have come to the conclusion that, though so very similar in most characters, 

 the two species must be separated on account of the invariably difi:erent characters of 

 the abdomen and orenital segment. 



E. similis is constantly rather larger than E. antarctica, 8"6 mm.-8*8 mm., and 

 more robust, the head flat and rostrum small, but strong and directed forwards and 

 rather upwards. The cephalothorax is two and a half times as long as the abdomen. 

 The last thoracic segment is produced forwards, slightly triangular shaped, with evenly 

 rounded margin, no spine, but a bunch of long hairs on each side. The abdominal 

 segments, of which the genital is twice as long as the next, are covered with fine hairs, 

 nowhere with large bunches, and the posterior distal margins have only very small 

 teeth, not large, as in antarctica. Furca with, on each side, a very short dorsal bristle, 

 the ventral accessory bristle not geniculated at the base, though bent outwards, its 

 length not more than about half of the two long tail bristles (next to the innermost). 



VOL. IV. M 



