166 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
EUCALANUS Dana. 
Anal segment and furca fused; furca asymmetrical. Mandible of female longer than maxilla and 
more than two-thirds as long as fourth pair of feet; its second basal joint forms with outer ramus a 
cylindrical body, with which the very small inner ramus articulates much further proximally than 
outer ramus. Inner ramus of posterior maxillipeds longer than first or second basal joint. First pair 
of feet with 3-jointed outer and 2-jointed inner ramus. Fifth pair of feet wanting in female; in male 
both of these feet are uniramous, the left 4-jointed, the right 1 to 4 jointed or lacking. 
Female: Trunk usually elongated; head fused with first thoracic segment, two last thoracic 
segments less intimately united; head triangular, often elongated, with transverse dorsal furrow; 
rostrum ending in thin threads; abdomen short, with 3 or 4 segments; genital segment, symmet- 
rical; anterior antennae reaching beyond end of body, sometimes of asymmetrical lengths, 23-jointed 
owing to fusion of first and second and of eighth and ninth joints; the first joint elongated, the last 
3. JEucalanus attenuatus Dana ; female; dorsal aspect. 
After Giesbrecht. 
4. Eucalanits monachus Giesbrecht male; a, dorsal 
aspect; b, fourth foot; c, left fifth foot. 
joint longer than penultimate; sesthetasks long and delicate; bristles usually plumose, those of 
terminal joints in part with long and sometimes gorgeously colored plumes; inner ramus of posterior 
antenna; longer than outer ramus, sometimes more than twice as long, the latter 7 or 8 jointed; 
proximal outer marginal lobe of maxilla; strongly projecting, second basal joint elongate, inner 
ramus distinctly jointed, outer ramus relatively small ; anterior maxilliped with a long, plumose outer 
marginal bristle; inner ramus of posterior maxilliped relatively loug and provided with long bristles; 
feet short, outer ramus 3-jointed; inner ramus of first pair 2-jointed, of remaining pairs 3-jointed. 
Male: Trunk shortened; peculiarities in form of head of female not apparent; abdomen of 5 seg- 
ments ; furca and furcal bristles similar to those of female ; first 2 joints of anterior antenme separate, 
terminal joint abbreviated; bristles abbreviated, with rudimental plumes; sesthetasks enlarged and 
increased in number; posterior antenme stouter than in female, part of bristles absent; mandibular 
