COPEPODS OF THE "WOODS HOLE REGION 



421 



Figure 264. 



AleMon gracilis: a. Female, dor- 

 sal ; 6, maxilliped 



FeiTiale. — Carapace elliptical, longer than wide, the median lobe 

 squarely truncated; fourth segment nearly as wide as the genital 

 segment and half as long; dorsal plates strongly curved, the convex 

 sides outward, the distal ends squarely truncated. Genital segment 

 half the width of the carapace, widest at the center, each posterior 

 corner a stout conical process 

 reaching beyond the tip of the 

 abdomen and sparsely set with 

 spines. Abdomen 2-segmented, 

 basal segment with a long proc- 

 ess at each posterior corner; 

 horny claws on the first three 

 exopods larger than in gldber. 

 Total length, 9-10 mm. 



Male. — Carapace orbicular, 

 a little wider than long ; fourth 

 segment as wide as the genital 

 segment; rudiments of dorsal 

 plates projecting laterally. 

 Genital segment small and 

 elliptical, widest at the center 

 with convex lateral margins, 

 and with no spines or processes 

 at the posterior corners ; a pair of leg rudiments on the ventral sur- 

 face near the lateral margins. Abdomen 2-segmented, the segments 

 about equal. Total length, 5-6 mm. 



Remarks. — This species can be recognized by the strongly curved 

 dorsal plates of the fourth segment in the female and the smoothly 

 rounded genital segment of the male. It is fairly common as in- 

 dicated by the number of hosts. 



ALEBION FUSCUS Wilson 



Figure 265 



Alebion fusctis Wilson, Proc. U. S. Nat. Mus., vol. 59, p. 2, pis. 1, 2, 1921. 



Occurrence. — Found on the outside surface and fins of the dusky 

 shark at Menemsha Bight, Marthas Vineyard. 



Distribution. — Not found outside the present area. 



Color. — Body a rich reddish brown, deepening into black in 

 preservatives ; eye dark brick red ; egg strings dark brownish gray. 



Female. — Carapace elliptical, longer than wide; median lobe 

 squarely truncated posteriorly and armed at each posterior corner 

 with three large spines; fourth segment as wide as genital segment, 

 but only a fourth as long, dorsal plates semielliptical, outer margins 

 strongly convex, inner margins straight, separated by a deep narrow 



