FREE-SWIMMING COPEPODS OF THE WOODS HOLE REGION. 
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7. Calocalanus pavo Dana; female, dorsal aspect. After Giesbrecht. 
Female: Head fused with thorax, fourth with fifth thoracic segment; rostrum terminating in 
soft filaments; abdomen short; furca sometimes asymmetrical, provided with gorgeously plumed 
setae; antennae extending beyond the end of body, 25-jointed, but with obliterated boundary between 
first and second and between eighth and ninth joints; many of the bristles long, pigmented or 
beautifully plumose. Posterior antennae with rami of equal length, or with shorter outer ramus. 
Mandible with but slightly dilated blade and small, sac-shaped appendage on proximal joint of 
inner ramus; maxillae and maxillipeds similar to those of calanm; inner ramus of iirst foot 2-jointed, 
of second to fourth foot 3-jointed. 
Male: Head distinctly separated from first thoracic segment; abdomen with 5 segments, furcal 
bristles less richly plumose; anterior antennae abbreviated; joints 1 and 2, 3 to 6, and 24 and 25 are 
fused, the twenty-fifth shortened; bristles reduced, aesthetasks powerfully developed. Peculiarities 
of succeeding appendages similar to those of Paracalanus. 
7. Calocalanus pavo Dana. 
Female : Abdomen with 2 segments ; genital segment onion-shaped ; furca and furcal bristles 
symmetrical. Terminal joint of anterior antennae 5 times as long as penultimate and more than 7 
times as long as twelfth joint. Outer ramus of posterior antennae nine-tenths as long as inner ramus; 
Coloration : Rather transparent, with red pigment, variable in amount but never very abundant. 
Length of female, 0.8 to 1 mm. ; of male, 0.91 to 1 mm. 
Numerous specimens of this species were taken in the Gulf Stream at 6 a. m., July 29, 1899, about 
70 miles south of Martha’s Vineyard. This species has been frequently taken on the coasts of Europe 
and also in the Pacific Ocean (west of South America, between 10° and 55° S., 108° W., and at Hong- 
kong), but its presence in the Western Atlantic has not been noted hitherto. 
CALOCALANUS Giesbrecht. 
First pair of feet without an inner marginal bristle on the second basal joint; the proximal 
portion of outer margin of last joint of outer ramus in fourth pair more than twice as long as distal 
portion; outer margin of outer rami not denticulate; terminal bristle of outer ramus in third pair 
longer than end joint; second joint of the inner ramus of first pair with 4 bristles; third joint of 
inner ramus of second pair with 7 bristles. Abdomen of female with 2 or 3 segments; last joint 
of anterior antennae at least twice as long as penultimate joint. Fifth pair of feet of female 3 or 4 
jointed; right fifth foot of male 4-jointed, left 5-jointed. 
