COPEPODS OF THE WOODS HOLE REGION 



323 



head and fifth segments rounded; urosome, including the caudal 

 rami, about half the length of the metasome, the posterior margins 

 of all its segments except the last serrate on the ventral surface; 

 genital segment dilated anteriorly; caudal rami very variable in 

 length, from one to four times the length of the anal segment, finely 

 ciliated on their inner margins. First antennae 17-segmented, nearly 

 reaching the posterior margin of the head. Eami of the first four pairs 

 of legs 3-segmented, the end segments of the exopods in some speci- 

 mens with 2, 3, 3, 3, spines; in other specimens with 3, 4, 4, 4 spines. 

 Basal segment of fifth leg wider than long, with a plimiose seta at 

 its outer distal corner ; distal segment short and narrow with a long 

 apical seta and a very short inner 

 spine. Semen receptacle made up 

 of a short anterior transversely el- 

 liptical or heart-shaped portion in 

 the center of the segment, and a 

 posterior narrow band extending 

 nearly across the segment. Total 

 length, 1-2 mm. ; rarely, 5 mm. 



Male. — Metasome narrow oval, 

 the greatest width (close to anterior 

 margin of head) to the length as 

 3:7; cephalic segment longer than 

 the rest of the metasome and 

 broadly rounded anteriorly; fifth 

 segment nearly as wide as the fourth 

 and produced laterally into sharp 

 angles; genital segment consider- 

 ably swollen anteriorly and nar- 

 rowed posteriorly; abdomen 4-seg- 

 mented, first and fourth segments 

 longer than second and third. First 

 antennae twice hinged, the termi- 

 nal portion made up of three segments, of which the one next the 

 hinge is very short, while the middle one is elongated. The fourth, 

 fifth, and sixth segments are very short and closely crowded, the ninth 

 segment is abruptly widened, and the following segments taper 

 gradually to the distal elbow. The second antennae, mouth parts, 

 and swimming legs are like those of the female. In the fifth legs the 

 distal segment is much wider but the setae and spine are the same; 

 rudimentary sixth legs are present at the posterior corners of the 

 genital segment. Total length, 0.8-1.5 mm. 



Remarks. — Sars has substituted the name vulgaris given by Koch to 

 this species for the varietal name viridis given by Jurine to one form 

 of his species Monoculus quadricorrds. American authors have re- 



FiGURE IQ'l.—CytloiJS viridis: a, Male, 

 dorsal ; h, male, first antenna ; c, male, 

 fifth and sixth legs ; d, female, fifth 

 leg 



