PUERTO RICAN COPEPODS — GONZALEZ AND BOWMAN 269 



Key to Females of the Inshore Puerto Rican Species of Oithona 



1. Re3 of P4 with 3 outer setae; anal segment short, about half as long as 



preceding segment; Al reaches about to middle of Ped Seg 1; Ri of PI 



2-segmented O. simplex Farran 



Re3 of P4 with 2 outer setae; anal segment subequal to preceding segment; 

 A 1 reaches beyond Ped Seg 1; Ri of PI 3-segmented 2 



2. Head with dorsal ocular lenses; genital segment with transverse dorsal 



ridge; P5 with 2 terminal setae O. oculata Farran 



Head without dorsal lenses; genital segment without dorsal ridge; P5 with 



1 terminal seta 3 



Head rather pointed; prosome about 1.5 times as long as urosome, with 



spots of blue pigment on ventral surface; B2 of Md with 2 heavy blunt 



terminal setae; egg sacs compact, with about 8 eggs in each. 



O. hebes Giesbrecht 



3. Head truncate; prosome about 1.2 times as long as urosome, without ventral 



pigment; B2 of Md with long pointed terminal seta armed with coarse 

 setules; egg sacs loose, with more than 20 eggs in each. 



O. nana Giesbrecht 



Oithona hebes Giesbrecht 



Figures 19, 20a-h 



Oithona hebes Giesbrecht, 1891, p. 475; 1892, pp. 538, 549, pi. 34, figs. 8-9.— 

 Grandori, 1912, p. 15.— Farran, 1913, p. 191 (key).— Rosendorn, 1917, 

 p. 44.— Pesta, 1921, p. 551, fig. G5.— Kiefer, 1929, pp. 9-10; 1936, pp. 320- 

 322, figs. 1-5.— Rose, 1933, p. 280, fig. 354.— Lindberg, 1950, p. 274 (key). 



[?1 Oithona ovalis Herbst, 1955, pp. 214-215, figs. 27, 28a-c.— Bjornberg, 1963, pp. 

 76-77. 



Oithona minuta T. Scott. — Coker and Gonzalez, 1960. 



[not] Oithona hebes Giesbrecht. — Wilson, 1942, p. 196. 



Female. — Length 0.53-0.56 mm. Prosome: urosome = about 1.5. 

 Prosome oval, ^\^dest at posterior end of cephalosome. Head rather 

 pointed anteriorly. Rostrum absent. Last 3 urosome segments 

 subequal. Caudal ramus about 3 times as long as wide; lateral 

 marginal seta inserted at proximal K of margin, 0.75 as long as lateral 

 apical seta; relative lengths of apical setae (lateral apical seta =1) 

 1:3.0:4.7: 2.4; dorsal seta = 2.5. A 1 reaches anterior margin of PedSeg 

 2. B2 of Md bears 2 heavy, equal setae, armed on margins with short 

 setules; Ri bears 5 setae. Re of P1-P4 armed as follows: 

 Outer seta: 1-1-3, 1-1-3, 1-1-3, 1-1-2. 

 Inner setae: 0-1-4, 1-1-5, 1-1-5, 1-1-5. 



Distal inner seta of Ri2 of P4 very robust. P5 with single long 

 terminal seta. 



Male, — Length 0.48-0.54 mm. Prosome :urosome = about 1.4. 

 Head wider than in female, truncate anteriorly. Al usually folded 

 in characteristic position as in figure 20a. A2, segment 3 relatively 

 longer and narrower than in female. Setae on B2 of Md somewhat 

 weaker than in female. 



