3()6 BULLETIN 158, UNITED STATES NATIONAL MUSEUM 



End segment of first exopod with 2 apical plumose setae and 1 

 slender outer spine; each fifth leg tipped with 3 short 



spines natahs (p. 306) 



2. Rostrum rounded at its tip, with a pair of subterminal setae; 

 inner spine of end segment of first endopod curved and 



acuminate ignaea (p. 307) 



Rostrum squarely truncated, with a pair of terminal juxtaposed 



spines ; inner spine of first endopod straight and blunt 



jousseaumei (p. 308) 



METIS NATANS (Williams) 

 FlQtIBE 183 



Ilyopsyllus natans Williams, 37th Ann. Rep. Comm. Inland Fisheries Rhode 

 Island, p. 73, pi. 1, 13 figs., 1907. 



Occurrence. — Obtained by Rathbun in a surface tow from the end 

 of a wharf at Newport, R. I., July 29, 1880. 



Distribution. — Wickford and Charlestown Pond (Williams). 

 Color. — Body orange-red, becoming very deep and even brownish 

 in some parts, in others changing to a straw yellow and becoming 

 more transparent. All the segments except the ce- 

 phalic appear banded, being deeper in color through 

 the middle and becoming lighter anteriorly and 

 posteriorly. Tlie four posterior segments are nearly 

 ^ uniform in color; the internal organs show dark 



brown beneath the orange-red; the appendages are 

 yellow. There are two irregular longitudinal series 

 of blood-red dots running through the metasome on 

 either side of the midline. The eye is very dark 

 blood red, with three clear lenses, one on each side 

 and one in front at the base of the rostrum. 

 (Rathbun.) 

 Female. — Cephalic segment not so convex dorsally 

 b as in the two following species, but still strongly 



Figure 183.— arched: rostrum large, thistle-shaped, and squarely 



Metis natans : a, ' *= ' . . • t i. i 



Female, fifth truncated at the apex, where it carries two ciliated 

 leg ; b, male, ^^^ movable spiucs, curved downward ; caudal rami 



fifth leg . -11 



short and broad, the inner terminal seta as long as 

 the body, its proximal half broadened and naked, its distal half 

 abruptly tapered and fringed with short cilia on the outer margin. 

 First antennae 6-segmented, the two basal segments well separated, 

 the aesthetask on the third segment jointed twice near its base. 

 Basal segment of second antenna longer than the second segment, 

 the end segment with five apical setae and a spine on the dorsal 

 surface near the base. Fifth legs fused across the midline, each 

 3-lobed, the lobes constricted at the base and bluntly rounded at 

 the tip, the outer one only bearing a filiform seta. Total length, 

 0.45-0.5 mm. 



