472 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



merited, basal segment the longer; caudal rami short, cylindrical, 

 unarmed. First antenna 11-segmented and straight, the basal seg- 

 ments scarcely enlarged and without claws; second antenna 4-seg- 

 mented, uncinate. Basal segments of maxillipeds fused on the mid- 

 line and projecting downward and forward; terminal claws turned 

 back dorsally and parallel with each other. First four pairs of legs 

 biramose, rami 3-segmented; fifth pair uniramose, 1-segmented. 



Male. — Head and free thorax similar to that of the female; fifth 

 segment relatively small and forming a sort of waist between the 

 fourth and genital segments. The latter as wide as the fourth seg- 

 ment and more than twice as long; abdomen 4-segmented, segments 

 diminishing backward. Caudal rami foliaceous and armed with 

 plumose setae; antennae, mouth parts, and swimming legs similar 

 to those of the female. A single species. 



Genotype. — Eudactylmella alba, new species. 



EUDACTYLINELLA ALBA, new species 

 Plate 36 



Occurrence. — Ten females and a male were found on the gills of a 

 sting ray {Dasyhatus inarinibs), August, 1924; the female holotype 

 is U.S.N.M. No. 56667. Four females were taken from the nostrils 

 of another sting ray, July, 1926, both fish captured in the fish nets 

 on Marthas Vineyard. 



Color. — Body a clear creamy white, without pigment markings. 



Female. — Carapace ovate, widest at the posterior margin, with 

 nearly straight sides, and a knoblike rostrum at the center of the 

 anterior margin. Second segment one-fourth wider than the cara- 

 pace, with convex lateral margins ; third, fourth, and fifth segments 

 diminishing regularly in width, but scarcely at all in length. Geni- 

 tal segment abruptly reduced to half the width of the fifth segment 

 but exceeding the latter in length. Abdomen 2-segmented, basal seg- 

 ment the longer and wider, anal segment with a lateral sinus on 

 either side, indicating a fusion of two segments. Caudal rami only 

 a third the length of the anal segment, and wholly without setae 

 or spines. 



First antenna slender and 11-segmented, the basal segments 

 scarcely enlarged and armed with setae only, the whole antenna in 

 a straight line and not geniculate. These antennae are thus very 

 different from those of Eudactylina and Eudactylinodes. Second 

 antenna 4-segmented, the third segment the longest, the fourth seg- 

 ment tipped with a stout claw, as long as the segment itself; at the 

 base of the claw on the inner margin of the fourth segment are 

 two small spines. Mandibles very long, slender, and cylindrical, 

 with a pectinate blade at the tip; first maxilla short and dactylose, 



