292 BULLETIN" 15 8, UNITED STATES NATIONAL MUSEUM 



all these spines are coarse, irregular, and bluntly rounded at their 

 tips. Mandibular palp minute and 1-segmented ; second maxillae 

 stout, with two lobes inside the terminal claw ; maxillipeds so minute 

 as to be easily overlooked, each made up of a vertical lamella, armed 

 with a basal nodule and two curved claws. 



The first four pairs of swimming legs have 2-segmented endopods, 

 the segments about equal in length, and 3-segmented exopods, all 

 the rami tipped with exceptionally long and slender setae. In the 

 first legs each ramus has one such long seta, in the second and third 

 legs two, while in the fourth legs the endopod has two and the 

 exopod four, nearly four times the length of the exopod itself. The 

 formulae of the spines and setae on these swimming legs are as fol- 

 lows: First exopod, 1-0, 1-0, 1-3; first endopod, 0-0, 0-2; second 

 exopod, 1-0, 1-0, 1-3; second endopod, 0-0, 0-4; third exopod, 1-0, 

 1-0, 1-3; third endopod, 0-0, 0^; fourth exopod, 1-0, 1-0, 1-A; 

 fourth endopod, 0-1, 0-4. Each fifth leg consists of a small lamella 

 with four setae, but without any distinction of parts except that the 

 outer seta is on a knoblike projection removed from the others, which 

 probably represents the outer process of the basal segment. 



Male. — Body smaller than that of the female, but very similar in 

 all its proportions. First antennae not geniculate ; second antennae, 

 mouth parts, and legs without any sexual modifications; fifth legs a 

 simple lamella without the outer process and armed with four fili- 

 form setae; sixth leg rudiments present on the anterior half of the 

 genital segment and consisting of a simple lamella smaller than that 

 of the fifth legs and armed with three tiny hairs. 



Remarhs. — The glasslike transparency and consistency of this spe- 

 cies are its chief characteristic, as well as the peculiar form of the 

 end segment of the second antenna. During all the time the living 

 copepods remained under observation they continued to lie on one 

 side and did not assume an upright position at all. 



Family TACHIDIIDAE 



Genus CLYTEMNESTRA Dana, 1847 



Metasome considerably depressed, all its segments, except the fifth, 

 with angular projections at the posterior corners; urosome 4-seg- 

 mented in female, 5-segmented in male; genital segment divided; 

 anal segment as long as penultimate segment ; caudal rami short and 

 wide, apical setae scarcely as long as the rami. First antennae 7- or 

 8-segmented; exopod of second antennae degenerate, replaced by 

 setae; first leg with 1-segmentcd exopod and 3-segmented endopod; 

 both rami of second, third, and fourth legs 3-segmented; fifth legs 

 2-segmented, segments narrow and elongate. One species only. 



