190 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



the anterior (ventral) surface with rows of small spinules running 

 in many directions. Total length, 0.4-0,6 mm. 



Male. — Considerably smaller than the female but of similar form; 

 fifth segment with even more prominent epimeral plates; genital 

 segment divided, both halves and the two basal segments of the 

 abdomen with small epimeral plates; caudal rami like those of the 

 female. Rostrum shorter and wider and fringed with minute hairs ; 

 first antennae strongly prehensile, the fifth and sixth segments swol- 

 len into the hand of a chela, the dactylus being formed by the last 

 two segments. In pairing the male extends these antennae their 

 full length laterally and grasps the female on the dorsal surface in 

 the groove between the cephalic and second segments with the claw 

 of each chela. 



The first legs are more slender than those of the female, and the 

 exopod is not enlarged at the tip; the exopods of the third and 

 fourth legs are armed with rows of small spinules on the anterior 

 surface, but neither ramus shows any sex modification. In the fifth 

 legs the basal expansions are much reduced in length but extend 

 inward to the midline where the two are fused together; each is 

 armed with two large setae widely separated; the distal segment 

 has two terminal setae, three on the outer and one on the inner 

 margin, all about equal in size. Total length, 0.25-0.35 mm. 



Remarks. — This copepod was very abundant in the sand of 

 Katama Bay ; in spite of its depressed form it is very active, crawls 

 about over the sand grains rapidly, and can swim with considerable 

 agility. The ovisac is more than half the size of the body and 

 extends far beyond the tips of the caudal setae. 



Genus ZAUS Goodsir, 1845 



Body short, broad, and rather strongly depressed ; metasome much 

 wider than urosome, its segments except the fifth expanded laterally 

 into epimeral plates; anterior segments of urosome also expanded 

 laterally ; genital segment divided ; urosome 4-segmented in female, 

 5-segmented in male; caudal rami short and lamellar. First an- 

 tennae 9-segmented in female, 6-segmented and chelate in male; 

 maxillipeds stout and strongly chelate. First exopod 2-segmented 

 and much longer than the endopod ; the latter and both rami of the 

 three following pairs of legs 3-segmented. Fifth legs 2-segmented, 

 the basal expansion short, but reaching the midline in the female, 

 almost lacking in the male; distal segment large and more or less 

 extended laterally beyond the body margin. Spines and claws of 

 the antennae and swimming legs conspicuously ciliate, dentate, or 

 pectinate. A single large ovisac. One species found here. 



