ABT. 15 COPEPOD CRUSTACEANS OF CHESAPEAKE BAY WILSON 31 



The inner ramus also ends in three long setae, with a tuft of five 

 others on the inner margin near the tip of the terminal joint. 



Chewing blade of the mandible broad and stout, with very irregu- 

 lar margins ; teeth small, blunt, and all about the same size except the 

 one at the inner corner, which is long, slender, sharply pointed, and 

 pectinate. Outer ramus of palp 4-segmented, inner ramus 2-seg- 

 mented, its terminal joint turned at right angles and ending in eight 

 setae, all about the same size and length. First maxillae broadly 

 laminate, with flattened and laminate setae; second maxillae 5-seg- 

 raented, the setae of the four basal segments mounted on long 

 papillae. Maxillipeds with stout basal joints and a 4-segmented 

 ramus. First four pairs of swimming legs with 3-jointed rami; 

 spines of the exopods with serrated margins; fifth legs uniramose, 

 4-segmented, each leg tipped with a pectinated spine much longer 

 than the terminal joint. 



Speci-flc characters of male. — Like the female but with the posterior 

 body symmetrical ; abdomen with four segments when fully matured, 

 in other respects like the young male figured in Plate 2 ; caudal rami 

 three to three and a half times as long as wide and without marginal 

 hairs. Right fifth leg uniramose, 4-segmented, with a terminal claw 

 much like that in the female ; left leg biramose, basipod and exopod 

 'S-segmented, endopod with a single bladelike segment, toothed along 

 its curved outer margin near the tip and at the center. First segment 

 of basipod with fingerlike processes on its inner margin, second 

 joint with coarse hairs on its inner margin; exopod tipped with 

 three or four small spines. 



Measureinents. — Length : Female, 1.5 mm. ; male, 1.2 mm. 



Occurrence. — Taken at every station in the bay except J, L, and 

 XJ ; never in any abundance but often with a percentage of less than 

 1. Definitely a winter form but sometimes present at other seasons ; 

 usually taken at or near the bottom in the bay but found only at the 

 surface in the outside ocean. 



Distribution. — Nova Scotia (Willey) ; Narragansett Bay (Wil- 

 liams) ; Sheepshead Bay, N. Y. (Sharpe) ; Woods Hole (Sharpe, 

 Fish). 



Remarks. — Williams and Sharpe obtained their specimens in sum- 

 mer, except those from Sheepshead Bay, which were taken in Sep- 

 tember. Fish said it was not a true summer species at Woods Hole, 

 but reached its maximum in fall, when it outnumbered all other 

 ■copepods. In Chesapeake Bay the maximum seems to be reached 

 still later in fall or early in winter, but even then the percentage 

 rarely gets above 5, all such instances being near the inner end of 

 the bay. The second antennae and mouth parts, with minor details 

 of the rest of the body, are figured in Plate 2 to supplement the 

 account here given. 



