54 PROCEEDINGS CF THE NATIONAL MUSEUM VOL. 113 
lobe oblanceolate, with acuminate apex. Left endopod bearing 4 
setae, medial setae arising proximally to others; produced at apex 
into median tooth and shorter outer tooth. Modified seta adjacent to 
endopod linear, moderately robust. 
Couor: Body transparent, with some internal brick-red blotches. 
Tyres: Holotype, female, USNM 104379; allotype male, USNM 
104380; and 3 paratypes (2 females, 1 male), from Thalass1a meadow, 
Canal de Magiieyes, La Parguera, Puerto Rico, collected June 9, 1959 
(holotype) and Nov. 25, 1959 (allotype and paratypes). 
The specific name rostratus (Latin “rostratus,’’ meaning beaked) 
refers to the large, conspicuous rostrum. 
The remarkably large rostrum distinguishes P. rostratus from all 
other species of Pseudocyclops. The rostrum is also strongly developed 
in the much smaller P. paulus, but not nearly to the degree that it is 
in P. rostratus. The acute posterior lateral corner of the second 
pedigerous segment is also useful for recognition, and the fifth legs of 
both sexes are unlike those of any other species. 
Pseudocyclops rubrocinctus, new species 
Ficures 9a-f, 10-11 
Fremae: Length, excluding caudal setae, 0.55-0.62 mm. Prosome, 
viewed dorsally, about twice as long as wide. Head separated from 
first pedigerous segment. Rostrum strong. Median sclerotization of 
third pedigerous segment present, but much shorter than in P. paulus. 
Fifth pedigerous segment with a few minute setae near posterior 
margin. 
Urosome about a third as long as prosome (urosome may be pro- 
portionately shorter in specimens in which the segments are con- 
tracted); posterior margins of segments minutely serrate. Genital 
openings with conspicuous sclerotization. Caudal rami about a sixth 
longer than wide, without hairs on inner margins. Next-to-innermost 
seta thicker and longer than others; proximal part with barbs on 
both margins, those on lateral margin more numerous. Proximal 
part of second-from-innermost seta with similar barbs on lateral 
margin; more numerous, longer, and more slender barbs on medial 
margin. 
Antenna 1 reaching middle of first pedigerous segment, composed 
of 18segments. Antenna 2 with 2 seta on basipod; exopod apparently 
3-seemented, setation as shown in figure lla; endepod with minor 
differences in setation from that of P. cokert. Gnathal lobe of man- 
dible with more teeth than that of P. cokeri; basipod of palp with 2 
setae; endopod segment 1 with 4 setae. Maxilla 1 with 4 setae on 
second basal segment; endopod with groups of 3 and 4 setae on medial 
