268 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



shorter than the others. The basal expansion is rather narrow and 

 carries five setae, the middle one the longest. Total length, 0.45- 

 0.55 mm. 



Male. — Somewhat smaller than the female and more slender, the 

 urosome nearly cylindrical; first antennae much enlarged, especially 

 the fourth segment, which is nearly circular in dorsal outline, with 

 a small sinus on its posterior margin. The aesthetask i^ attached 

 to this fourth segment and is as long as the four basal segments of 

 the antenna combined; the second, fourth, and sixth segments are 

 densely setose, the others only sparingly so. The first legs are simi- 

 lar to those of the female but more slender; the second and third 

 legs are modified as is usual in this genus. The exopods of these 

 two latter pairs of legs are stout and the terminal segments are bent 

 inward nearly at right angles to the long axis of the legs. Each end 

 segment is armed with six rather slender spines of very unequal 

 lengths and a short inner seta. The endopods scarcely reach the 

 lip of the basal exopod segment; the distal segment of the second 

 endopod is shorter than the basal segment and carries three elongate 

 apical setae and an inner spine. The latter is short and sharply 

 bent twice into an S-curve, blunt at its tip. The distal segment of 

 the third endopod is twice as long as the basal segment and is 

 obliquely truncated at its tip, with a row of four apical setae and 

 an outer spine. The latter is stout and curved slightly backward 

 at its tip, and looks like the thumb of a hand, the fingers of which 

 are the four apical setae; this resemblance to a hand has given 

 rise to the specific name. The fourth endopod also just reaches 

 the tip of the basal exopod segment ; its distal segment is three times 

 as long as the basal segment, and carries two apical and one inner 

 setae, and a minute inner spine. The end segment of the fourth 

 exopod has two apical setae, one inner seta, and three long and slen- 

 der outer spines, the two distal ones setose. 



The fifth legs are reduced to a narrow lamina reaching from the 

 lateral margin to the midline, and bearing six setae. The outer 

 seta is separated from the others and mounted on a small knob, 

 which represents the outer process of the basal segment. The next 

 two setae are close together and separated from the fourth and 

 represent the distal segment of the leg. The three remaining setae 

 represent the basal expansion; rudiments of sixth legs are also 

 present. Total length, 0.4-0.5 mm. 



Remarks. — This species is closely related to strdmii but is much 

 smaller and differs greatly in the details of the swimming legs, 

 especially the second and third pairs in the male. This copepod 

 was not washed out of the sand but was swimming freely in the 

 plankton. 



