FRESH- \VATEI^ Ci'CLOl'ID^: AND CALANID.IC. 75 



1 am rather disposeil to look upon C. ahijsHorum as a deep- 

 water variety of C. vicinm, the differences between the two 

 forms being merely matters of degree ; the most important point 

 is, perhaps, the length of the anterior antenna), which are de- 

 cidedly shorter and thicker in C. vicinus : the peculiar setose 

 armature of the anteunrc is seen, though more feebly, in C. vicinus : 

 the characters of the fifth feet, the abdomen, and caudal rami 

 are alike in both forms. 



5. Cyclops Scourfieldi, a. S. Brady (PI. IV.). 



1863. Ci/chps LeuckarUi, G. 0. Sars (20), pi. VI., figs. 6-8, 



p. 30 (not C. Letcekarti, Claus). 



Female. — Body slender, subtruncate in front and tapering 

 gradually backwards ; thoracic segments rounded off behind and 

 not produced into angles laterally ; the last segment smaller 

 than the rest, from which it is separated in front by a deep 

 constriction : first abdominal segment nearly as wide as the last 

 thoracic, slightly wider in front than behind, and longer than 

 the three following segments combined : caudal rami as long as 

 the two preceding segments, the innermost of the two median 

 tail-setse is the longest and equal to the length of the abdomen, 

 the other only slightly shorter ; the two lateral set^ short and 

 subequal ; between the principal seta and the inner lateral 

 there is a fifth seta of intermediate length ; marginal setse short 

 and situated not far from the middle of the furca. Anterior 

 antennae slender, reaching a little beyond the second cephalo- 

 thoracic segment, the last two Joints elongated and slender; the 

 fourth, seventh, and fifteenth joints are of medium length, all 

 the rest short, except the first and the last two, which are the 

 longest of all. The anterior maxilliped has the posterior margin 

 of the second joint minutely crenulated near the middle. All 

 four pairs of swimming feet have their branches three-jointed, 

 the last joint of the outer branch bearing only one lateral spine ; 

 spines long and slender, with ciliated margins : the terminal 

 joints of the inner branches are elongated and of peculiar shape, 

 being dilated at the apex, with produced, spine-like angles ; the 

 first three pairs have a single terminal spine, the fourth pair 



