PEREZ FARFANTE: KEV TO AMERICAN PACIFIC SHRIMPS, GENUS Trathypiitratu! 



5 mm 



Figure 3. — Telsons. A. Trachypenaeus fuscina sp. n., 

 5 33 mm carapace length, off Cocodrilo, Chiapas, Mexico. 

 B. Trnchypenaeus faoea Loesch and Avila, 9 37 mm car- 

 apace length, Ensenada de Garachine, Golfo de Panama, 

 Panama. 



sulci; terminal portion (from mesial base of 

 posteriormost spine to apex) from relatively 

 short to long, its length relative to its width at 

 base ranging from 1.60 to 3.70; telson armed 

 with four pairs of lateral spines, posteriormost 

 pair fixed and long, ratio length of spine/width 

 of terminal portion = 0.70 (iV27: 1-0.50); other 

 spines movable and strong, posterior pair (lo- 

 cated at lateral base of longer fixed spines) rel- 

 atively long, anterior two pairs (located poster- 

 ior to midshoulder of telson) small, but usually 

 visible with naked eye. 



Petasma (Figure 4 A, B) with large, hornlike, 

 distolateral projections, broad at base, curving 

 laterally, and opening dorsally near anterior 

 margin by long, transverse slit; posteroventral 

 wall of horns reflexed dorsally and produced for- 

 ward into membranous flap; distomedian projec- 



tions short, overhanging distoventral aperture 

 of petasma. Ventrolateral lobule of petasma al- 

 most entirely cornified, including ventral wall 

 of horns and dorsally reflexed lateral margin; 

 proximomedian portion of lobule with rather 

 flexible strip, tapering to base of distal two-fifths 

 of median margin, there ending where corneous 

 sclerite, curving mesially, reaches margin; soft 

 elliptical area immediately distal to corneous 

 section of margin. Dorsolateral lobule bearing 

 narrow rib along proximomesial third, rib broad- 

 ening proximally and turning mesially at prox- 

 imal extremity resembling golf club. Dorso- 

 median lobule with narrow, distally bifurcate rib 

 at base of distomedian projection, its length 

 about one-third that of lobule. Length of pe- 

 tasma — from apex of distomedian projection to 

 proximal margin of dorsolateral lobule — almost 

 one and one-fifth times its width at level of disto- 

 lateral projections. 



In males, posterior margin of sternite XIII 

 (Figure 4F) bearing large, elongate, subellipti- 

 cal to ovate median plate, latter with obtuse to 

 acute tip, and numerous marginal setae; anterior 

 half of sternite XIV with strong, subpyramidal 

 prominence, its anterolateral, ventromedially in- 

 clined edges often forming shelflike ridges. 



Appendix masculina (Figure 4C-E) thick, 

 subcircular in outline, its length along midline 

 subequal to maximum width, and produced into 

 two proximolateral prominences; dorsal wall 

 cornified, except for distal and lateral margins, 

 these, together with ventral wall, rather soft; 

 entire, broad, median border setiferous, setae 

 continuing on distal margin forming narrow 

 band. Dorsal base of endopod with corneous, 

 roughly trapezoidal sclerite, bearing strong me- 

 dian rib articulating distally with appendix 

 masculina; rib with small setiferous depression 

 on distal portion of ventral surface. Accessory 

 sclerite on dorsolateral margin of endopod. 



Thelycum (Figure 5A) with posterior part 

 bearing anterolateral, subtriangular, heavily 

 sclerotized projections; anterior part of sternite 

 XIV, with platelike base, projecting as median 

 prominence, and produced forward into pair of 

 lateral, elongate, tonguelike flaps, extending al- 



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