FREE-SWIMMING COPEPODS OF THE WOODS HOLE REGION. 
173 
to twenty-third are fused, the articulation being between the eighteenth and nineteenth .joint; 
in the outer ramus of left fifth foot the inner bristle is wanting, and second .joint is fused with third, 
which sometimes bears awl-shaped appendages; outer ramus of right fifth foot remains 3-jointed, and 
its two terminal .joints are modified to form a forceps, one limb of which is the terminal joint, the 
other the inerassated inner marginal bristle of the second joint. 
10. Centropages typicus Kroyer. 
Unpaired eye with ventral convexity; fifth thoracic segment with lateral hooks, which are not 
quite symmetrical in male; anal segment of male obsolescent; outer furcal bristle short, inserted 
near tip of margin, not plumose in male, awl-shaped ; genital segment of female with 4 thorn-like 
bristles: fourth abdominal segment with a knob-like swelling on right side; anterior antennas 
exceeding end of furca by about their last two joints; second joint sharply separated from first, at 
least twice as long as third; joints 3, 6, and 25 without proximal bristle; anterior margin of joints 1, 
2 b, and 5 with a tooth. Outer ramus of posterior antenme but little longer than inner. Rami of 
mandibles of about equal length. Second outer lobe of maxilla with a small plumose bristle; second 
inner lobe pyriform, with 3 bristles; second basal joint with 5 bristles. First joint of inner ramus 
and third to fifth of posterior maxillipeds each with 2 marginal bristles; second joint of inner ramus 
with 3 inner marginal bristles. Prong of second joint of outer ramus in fifth foot of male robust, longer 
11. Centropages hamatus Lilljeborg ; a , male, dorsal aspect ; b, female, dorsal aspect ; c, female, ventral aspect of abdomen ; 
d, male, fourteenth to twenty first joints of right anterior antennae ; e, male, right fifth foot ; /, female, fifth foot. 
than .joint, erect. Middle joints of male grasping antenna broad ( joints 13 and 14 broader than long)'; 
anterior border of joint 15 with a small tooth, joint 16 with a larger tooth ; second joint of right outer 
ramus of third and fourth foot in male with enlarged outer marginal bristle. Forceps of male grasp- 
ing foot stout; distal hook longer than proximal; outer bristle on end joint of left outer ramus short. 
Coloration: Not very transparent; with reddish-brown pigment variously distributed through 
the cephalothorax and abdomen, especially in neighborhood of mouth and insertions of posterior feet 
(also in the grasping antenna). 
Length of female, 1.6 to 2 mm. ; of male, 1.42 to 1.85 mm. 
This species is nearly always present in small numbers in the tow taken from the Fish Commis- 
sion’s wharf at Woods Hole and in the neighboring Vineyard Sound. Very abundant in tow from 
Plymouth Harbor and from the Gulf Stream 70 miles south of Marthas Vineyard. In the latter tow 
'the specimens were full of a dark blackish-blue pigment. 
