PSEUDOCYCLOPS COPEPODS—BOWMAN AND GONZALEZ Al 
for food. In support of Hutchinson’s suggestion, Fryer (1954) found 
clear-cut differences in the gut contents of Diaptomus laticeps and 
the smaller D. gracilis in Lake Windermere, England. It is possible 
that differences in food preference may enable the 4 species of Pseu- 
docyclops to live together without undue competition. A ciliate 
protozoan abundant among the Zhalassia leaves in the Canal de 
Magiieyes could often be seen in the guts of cleared specimens of P. 
cokeri, but was only rarely observed in the other 3 species. 
Pseudocyclops cokeri, new species 
FicureEs 1-3 
Frmate: Length, excluding caudal setae, 0.5-0.6 mm. Prosome 
stout; width, viewed dorsally, slightly more than half the length. 
Head fused with first pedigerous segment except in ventrolateral 
region, where partial suture is present. Rostrum prominent, but 
not so strongly developed as in other Puerto Rican species. 
Urosome about three-eighths as long as prosome in specimens 
with segments not telescoped. Genital opening with characteristic 
pattern of sclerotization (fig. id-e). Behind genital openings is a 
ring of thickened cuticle from which a membranous sleeve with 
minutely serrate free (posterior) margin extends backward. Caudal 
rami about a third longer than wide, without hairs on inner margins. 
Outer caudal seta subterminal, about as long as ramus; middle 2 of 4 
terminal setae with jointed bases; next-to-innermost seta longest, 
about 3 times as long as urosome, proximal half stout, distal half 
slender, the seta without barbs, plumose only on distal half of stout 
portion. 
Antenna 1 reaching about half the length of cephalothorax, com- 
posed of 15 segments. First segment bearing 3 conspicuous aesthetes 
about equal In length to the last 14 segments combined, 1 seta as 
long as the aesthetes, and several shorter setae. Remaining segments 
without aesthetes except terminal segment, which bears a single 
short one; relative lengths and setation of segments as shown in 
figure If. 
Basipod of antenna 2 consisting of 1 segment partially divided by 
incomplete suture, without setae. Exopod 2-segmented; proximal 
segment bearing 5 setae on medial border, 1 in middle of border and 
4 distally; distal segment with partial suture near base, bearing 
1 medial and 4 distal setae. Endopod 3-segmented; suture between 
second and third segments weak; setae as shown in figure 2a. 
Gnathal lobe of mandible only slightly expanded, with 3 strong 
and 2 small sclerotized teeth, and a nonsclerotized acuminate tooth. 
