PARASITIC COPEPOD CRUSTACEANS — LEWIS 105 



pedigeroiis segment ala. Third pedigerous segment width approxi- 

 mately twice the length, with knoblike swelling on lateral surface 

 forming attachment and articulation surface for third thoracic leg, 

 with pair of small, knoblike protrusions posteriorly, overlapping short 

 anterior end of fourth pedigerous segment Fourth pedigerous seg- 

 ment distinct from genital segment dorsally although fused ventrally; 

 segment small, slightly longer than wide, lateral surfaces distinct 

 ventrally although tapered into large ala. Ala extending laterally, 

 across dorsal surface of posterior end of lateral cephalothoracic region, 

 extending posteriorly and covering anterior third of genital segment. 

 Median posterior region of ala bilobed, with deep sinus separating 

 lobes. Second through fourth pedigerous segments of male (fig. 206) 

 free, lateral projection of second not as well developed as in female. 

 Third pedigerous segment as in female; ala of fourth pedigerous seg- 

 ment much smaller in male than in female, bilobed posteriorly although 

 without deep sinus, overlapping anterior end of genital segment. 



Female genital segment (fig. 20c) large, anterolateral corners rounded, 

 median anterior surface concave; lateral margins flatly convex, postero- 

 lateral surfaces lobate, projecting posteriorly almost to end of caudal 

 rami. Dorsal surface with platelike processes extending over most of 

 segment and overlapping part of abdomen. Medial posterior surface 

 forming place of attachment of large, orbicular projection (sixth seg- 

 ment of Wilson, 1907b) and pair of large, lobate laminae. Abdomen 

 1-segmented, projecting from ventral genital segment surface immedi- 

 ately posterior to attachment of orbicular projection and laminae (not 

 attached to orbicular projection but to genital segment). Proximal 

 end of abdomen broad, tapered sharply posteriorly. Caudal rami 

 arising from sharp taper of abdomen. Rami strongly flattened, outer 

 lateral portion folded, bearing 4 lightly pliunose setae from distal 

 region and minute setule medial to innermost seta. 



Male genital segment (fig. 20f/) slender, barrel-shaped, lateral regions 

 appearing slightly swollen, posterolateral regions each with slender, 

 knoblike area of heavy sclerotization distinct from rest of segment. 

 Fifth leg (fig. 20e) consisting of knob-shaped protrusion bearing 1 

 plumose and 2 naked setules, single, plumose setule present just lateral 

 to protrusion. Sixth leg (fig. 20/) a minute nodule bearing 2 naked 

 setules. Abdomen 2-segmented, arising from posteroventral genital 

 segment surface. First segment narrower anteriorly than posteriorly, 

 length approximately three-fourths the width, posterior end with 

 flattened, V-shaped outline. Second segment slightly longer than 

 first, outline irregular, lateral regions curved ventrally and more 

 heavily sclerotized than rest of segment, lateral posterior margins 

 angled, surfaces forming attachment for caudal rami. Caudal rami 



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